Direct answer
For the SimpliSafe Motion Sensor (Gen 2), event capture, cloud processing, phone permission, Focus/background rules and alert zones are separate layers. First, trigger one repeatable event and compare event timestamp with alert time.
What this covers
- SimpliSafe Motion Sensor (Gen 2) (Gen 2 — the serial number is inside the battery compartment)
- SimpliSafe Gen 3 system component; sensors reach the Base Station over SimpliSafe's own sub-GHz radio rather than Wi-Fi, so a router problem and a sensor problem are separate investigations. Monitoring plan, cellular backup and camera generation vary.
- The specific fault this record addresses: notifications are late, missing or excessive
What it does not cover
- ×The same symptom on a different SimpliSafe product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
The phone's operating system is holding or silencing the notification
What separates it The event exists in the app's history with the right timestamp, but nothing appeared on the lock screen — or it appeared much later, in a summary. Focus modes, scheduled summaries, per-app notification settings and battery optimisation all do this silently.
How to confirm Compare the event's timestamp in the history with when the phone showed it. A correct event and a late or absent alert puts the fault entirely on the phone, and nothing done to the device will change it.
- 2
The device is asleep between events to save power
What separates it The first alert after a quiet period is late and subsequent ones are prompt. Battery hardware sleeps its radio and takes time to wake, transmit and be processed.
How to confirm Trigger two events a minute apart. A slow first and prompt second is a wake-from-sleep delay and is a designed trade, not a fault.
- 3
Alert-type settings do not match what is being triggered
What separates it Some events notify and others do not, consistently by type — motion alerts arrive but person alerts do not, or vice versa. The app's own alert settings are layered per device, per zone and per event type.
How to confirm Compare the event types present in the history against the alert types enabled. This is the most common cause of 'missing' notifications and involves no fault anywhere.
- 4
Network delay between the device and the provider
What separates it Alerts arrive in bursts after a delay, several at once, rather than individually late. The device is queuing events it cannot deliver.
How to confirm Compare the reported signal strength and the event timestamps. Bunched delivery is a transport problem; evenly late delivery is a processing or phone problem.
- 5
Several people share the device and each has their own alert settings
What separates it One household member gets alerts and another does not, from the same device. Alert preferences are per user, not per device.
How to confirm Compare the settings on each phone rather than assuming the device is configured once for everyone.
- 6
The app has been force-stopped or restricted in the background
What separates it Alerts stop after the phone was cleaned up, updated, or put into a battery-saving mode. An app that cannot run in the background cannot present a push notification reliably.
How to confirm Check the phone's background activity and battery optimisation settings for the app specifically. Aggressive power management on some Android builds does this by default.
- 7
Duplicate alerts from more than one integration
What separates it Every event notifies twice, from the manufacturer's app and from a linked platform. Both are working correctly; nothing is broken.
How to confirm Disable notifications in one of the two rather than changing device settings.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- One repeatable, deliberate event — walk the same path at the same time — because a comparison needs a known trigger, not a remembered one.
- The timestamp of that event in the app's history, and the timestamp the phone displayed the alert. The gap between them is the single most diagnostic number on this page.
- Whether the event exists in the history at all. A missing event is a detection problem; a present event with no alert is a notification problem.
- The alert types enabled in the app, per device, compared against the event types actually being recorded.
- Whether other household members received the same alert, since preferences are per user.
- The phone's Focus, scheduled summary, per-app notification and battery-optimisation state at the time.
- The battery level and whether the device had been idle before the event.
Trigger one deliberate, repeatable event
ReversibleWalk a known path at a known time rather than waiting for something to happen. Every comparison below needs a trigger whose real time you know, and a remembered event will not do.
Check whether the event exists in the history at all
ReversibleThis splits the problem in half and costs one look. No event in the history means nothing was detected, and the detection record applies instead — no notification setting can deliver an alert for an event that was never recorded.
Compare the event timestamp with the alert timestamp
ReversibleA correct event time and a late or absent alert puts the fault on the phone or the push path. Both times late puts it on the device or the provider. This one comparison decides which half of the remaining steps is worth doing.
Audit the phone's own notification settings before the app's
ReversibleFocus modes, scheduled summaries, per-app permissions and battery optimisation each suppress alerts silently and are the most common single cause. Check them explicitly rather than assuming they are as you left them.
Compare enabled alert types against recorded event types
ReversibleAlert settings are layered per device, per zone and per event type. Motion recorded but person alerts enabled — or the reverse — produces exactly the reported symptom with nothing actually broken.
Test two events a minute apart
ReversibleA slow first alert and a prompt second is a battery device waking its radio, which is a designed power trade rather than a fault. Consistent lateness on both is a different problem.
Compare settings across every account that uses the device
ReversiblePreferences are per user. One person receiving alerts and another not is a settings difference on the phone, not a device fault, and changing the device will not fix it.
Change one setting at a time and retest with the same event
ReversibleSensitivity, zones and alert types interact. Changing several at once produces a result that cannot be attributed, which is how a working configuration gets tuned into a broken one.
Verify with the phone locked and away from home
ReversibleNotification behaviour differs between an unlocked phone on the home network and a locked phone on cellular data. Only the second test reflects how the alert will actually reach you.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- Gen 2 — the serial number is inside the battery compartment. SimpliSafe Gen 3 system component; sensors reach the Base Station over SimpliSafe's own sub-GHz radio rather than Wi-Fi, so a router problem and a sensor problem are separate investigations. Monitoring plan, cellular backup and camera generation vary.
- Range and coverage
- SimpliSafe states the Gen 2 sensor has a range of 35 ft and a 90° field of view, intended to cover an entire room from one location. Beyond 35 ft is outside specification and no sensitivity setting extends it.
- Mounting height
- SimpliSafe specifies mounting in a corner, 6 ft from the floor. It states a shelf is acceptable only if it is still 6 ft from the floor, sitting flat and with a clear view of the room. Height error is the most consequential installation mistake on this sensor.
- Pet discrimination
- SimpliSafe states the Gen 2 sensor is engineered to tell the difference between people and pets up to 60 lbs, using a more advanced PIR sensor and detection algorithm than the Gen 1. An animal heavier than 60 lbs is outside what that discrimination is specified for.
- Sensitivity
- Two modes — Standard and Pet — adjustable in the SimpliSafe app. This is a mode switch rather than a continuous slider, so the tuning options here are narrower and more predictable than on a camera.
- Generation
- Gen 1 and Gen 2 are genuinely different hardware: SimpliSafe attributes the 35 ft range, the 90° field of view, the 60 lb pet discrimination and the app-adjustable sensitivity to the Gen 2 specifically. Procedures and expectations do not transfer between them.
- Power path
- Internal or removable battery. Every capability that costs current — night vision, higher stream quality, longer recordings, frequent events — is paid for in runtime, so a change in behaviour after a settings change is usually a power consequence rather than a fault. Cold weather reduces usable capacity sharply.
- Radio
- A manufacturer-specific sub-GHz radio to the base station rather than Wi-Fi. It travels further through structure than Wi-Fi does and is unaffected by router changes — which means a Wi-Fi problem and a sensor problem are genuinely separate investigations here.
- Symptom boundary
- This record covers SimpliSafe Motion Sensor (Gen 2) when it notifications are late, missing or excessive. A different symptom on the same hardware, or this symptom on a different SimpliSafe product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Critical security or safety alerting is unreliable after the checks above. Consumer push notification is a best-effort service and should not be the only layer for anything that matters.
- !The device records events correctly and the provider consistently fails to deliver them, which is a service fault only the provider can see.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. SimpliSafe Support publishes this as "Motion Sensor Gen 2 False Alarms". SimpliSafe's own article for excessive or spurious motion events. What that article does not carry is the model boundary — it is written for a product line, and Gen 2 — the serial number is inside the battery compartment is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
How far does the Motion Sensor Gen 2 reach?+
SimpliSafe specifies 35 ft with a 90° field of view, designed to cover a whole room from one corner. A subject beyond 35 ft is outside specification, and that is the answer to most 'it misses people at the far end' reports — sensitivity does not extend range.
How high should I mount it?+
SimpliSafe specifies a corner, 6 ft from the floor. A shelf is acceptable only if it is still 6 ft up, flat, and with a clear view of the room. Height is the single most consequential thing about installing this sensor, because the detection zones fan outward from it.
Will my dog set it off?+
SimpliSafe states the Gen 2 distinguishes people from pets up to 60 lbs, using a more advanced PIR sensor and algorithm than the Gen 1. Above 60 lbs that discrimination is outside what it is specified for — and mounting height still matters, because it determines whether the animal is below the lowest zone.
How do I change the sensitivity?+
In the SimpliSafe app, between Standard Mode and Pet Mode. It is a two-position mode rather than a continuous slider, so there is no partial adjustment to hunt for — which also means placement and height carry more of the load here than on a camera.
How is the Gen 2 different from the Gen 1?+
SimpliSafe attributes to the Gen 2 specifically: a 35 ft range, a 90° field of view, people-versus-pet discrimination up to 60 lbs, and app-adjustable sensitivity. They are genuinely different hardware, so a figure or a procedure from one does not transfer to the other.
Alerts arrive minutes late. Where is the delay?+
Compare the event's timestamp in the history with when the phone showed it. If the event time is correct, the delay is entirely on the phone or the push service, and nothing you change on SimpliSafe Motion Sensor (Gen 2) will help. If the event time itself is late, the delay is at the device or the provider.
I get no alerts but the recordings are all there.+
That is the cleanest possible split: detection and recording work, delivery does not. Check the phone's Focus modes, scheduled summaries and per-app notification permission first — they suppress alerts without any indication that they are doing so.
Why is the first alert of the day always slow?+
A battery device sleeps its radio between events and needs time to wake, associate and transmit. The first event after a quiet period pays that cost; the second one a minute later does not. Testing two events a minute apart confirms it in under two minutes.
My partner gets the alert and I do not.+
Alert preferences are per user account, not per device. Two phones on the same device routinely have different settings, and the device is configured correctly for one of you. Compare the two phones rather than changing the device.
Alerts arrive several at once after a gap.+
Bunched delivery means the device queued events it could not deliver and then flushed them. That is a transport problem — signal or provider — rather than a notification setting. Evenly late delivery would point somewhere else entirely.
Does Do Not Disturb block these?+
Yes, along with Focus modes, scheduled notification summaries, per-app permission changes and battery optimisation. All of them suppress alerts silently, which is why the phone should be audited before the device.
I get every alert twice.+
You almost certainly have the manufacturer's app and a linked platform both notifying. Nothing is broken. Turn notifications off in one of them rather than changing anything on the device.
Alerts stopped after I updated my phone.+
Operating system updates reset per-app notification permissions and background activity limits more often than people expect. Check the app's notification permission and its background activity allowance specifically — a restricted app cannot deliver a push reliably.
How do I test this properly?+
Walk one deliberate, repeatable path at a known time, with the phone locked and on cellular data rather than Wi-Fi. Anything less realistic than that produces a result that does not match how the alert will actually reach you.
Should I reinstall the app?+
Rarely necessary and it loses your per-device settings. Work the timestamp comparison first — it identifies the layer in one step, and a reinstall that happens to fix things teaches you nothing about which layer was at fault.
Does this answer apply to every SimpliSafe model?+
No. It is scoped to Gen 2 — the serial number is inside the battery compartment. SimpliSafe Gen 3 system component; sensors reach the Base Station over SimpliSafe's own sub-GHz radio rather than Wi-Fi, so a router problem and a sensor problem are separate investigations. Monitoring plan, cellular backup and camera generation vary.
What should I record before troubleshooting notifications or alerts?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing notifications, alerts. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Preserve critical security/safety alerts and privacy.
Answer for the exact device and software version shown above.