Direct answer
For the ASUS Zenbook S 14 UX5406, accessory state, competing hosts, driver/firmware and radio hardware should be isolated. First, remove competing pairings and test nearby with both devices charged.
What this covers
- ASUS Zenbook S 14 UX5406 (UX5406 series)
- ASUS PC; full model code determines BIOS, GPU mode, USB-C video, charger and driver package.
- The specific fault this record addresses: Bluetooth is missing, will not pair or disconnects
What it does not cover
- ×The same symptom on a different ASUS 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 accessory is connected to another device
What separates it It powers on and does not appear in the computer's scan, with a phone or tablet nearby that it has been paired with before.
How to confirm Turn Bluetooth off on other nearby devices, or disconnect there explicitly, then retry. This is the most common cause by a wide margin.
- 2
The accessory is not in pairing mode
What separates it It is powered on but does not appear in the scan.
How to confirm Pairing mode is a deliberate button hold, distinct from switching on, and is normally indicated by a specific flashing pattern.
- 3
A stale pairing is preventing reconnection
What separates it A device that previously worked will not reconnect, and appears in the list as not connected.
How to confirm Remove the device from the computer's list entirely and pair it again from scratch.
- 4
2.4 GHz interference is disrupting the connection
What separates it Stuttering audio or laggy input, worse near a router, a USB 3 device or a crowded desk.
How to confirm Bluetooth shares the 2.4 GHz band with Wi-Fi, and USB 3 ports are a known source of interference. Moving the receiver or the device often resolves it.
- 5
The Bluetooth service or driver has stopped
What separates it Bluetooth disappears from settings entirely, or no devices can be found at all.
How to confirm Restart the machine properly, and check the adapter is enabled and its driver present.
- 6
The accessory's battery is low
What separates it Intermittent connection or a device that disconnects shortly after connecting.
How to confirm Low battery causes connection instability well before the device stops working entirely.
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.
- Whether the accessory appears in the computer's scan at all.
- Whether it is paired to a phone or tablet nearby that it might be reconnecting to.
- Whether the problem is failure to pair, or an unstable connection after pairing.
- The accessory's battery level.
Turn Bluetooth off on nearby phones and tablets
ReversibleAccessories reconnect to the last device the instant they power on, and the computer then never sees them. This is the most common cause.
Put the accessory into pairing mode deliberately
ReversibleThat is a specific button hold with its own indicator pattern, not simply switching it on.
Remove a stale pairing from the computer's list and pair again
ReversibleA previously working device that will not reconnect usually needs the old pairing cleared first.
Move away from routers and USB 3 devices for one test
ReversibleBluetooth shares 2.4 GHz with Wi-Fi, and USB 3 ports are a documented interference source.
Charge the accessory and retest
ReversibleLow battery causes instability well before the device stops working outright.
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
- UX5406 series. ASUS PC; full model code determines BIOS, GPU mode, USB-C video, charger and driver package.
- Tier — premium ultrabook AI PC (Windows 11)
- A thin premium Windows 11 ultrabook (Copilot+ AI PC with an NPU) and an OLED display — for everyday and office work with long battery. Not a gaming machine.
- Copilot+ AI + thin thermals
- Copilot+ AI features need Windows updates/rollout (a missing one is software timing, not a fault). As a thin ultrabook it can warm and throttle under sustained load, which is expected.
- OLED care & ports
- OLED can show temporary image retention that clears (use dark mode/auto-hide taskbar). USB-C/Thunderbolt plus usually HDMI/USB-A.
- 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.
- Symptom boundary
- This record covers ASUS Zenbook S 14 UX5406 when it Bluetooth is missing, will not pair or disconnects. A different symptom on the same hardware, or this symptom on a different ASUS product line, has its own record with its own causes and its own cited source.
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. ASUS Support publishes this as "Product support". Official ASUS manuals, BIOS, drivers and repair support. What that article does not carry is the model boundary — it is written for a product line, and UX5406 series 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
My ASUS Zenbook S 14 OLED shows a faint taskbar ghost.+
That is temporary OLED image retention — a faint remnant of a static element like the taskbar — and it normally clears on its own; it is not permanent burn-in in ordinary use. Reduce it by enabling Windows dark mode, auto-hiding the taskbar, using a shorter screen-off timer, and letting ASUS's OLED Care / Windows pixel-refresh run. Permanent burn-in requires very prolonged static content. Occasional temporary retention is normal OLED behaviour.
My headphones won't show up on my laptop at all.+
Turn Bluetooth off on your phone first. Headphones reconnect to the last device they were paired with the moment they power on, so they are already busy and the laptop never sees them advertising. Then put them into pairing mode deliberately — that is a specific button hold with its own flashing pattern, not just switching them on.
My Bluetooth mouse stutters near my desk.+
That is usually 2.4 GHz interference. Bluetooth shares the band with Wi-Fi, and USB 3 ports and their cables are a well-documented source of interference in exactly this range. Moving the receiver to a port further away, or using a short extension to get it away from the machine, normally fixes it.
Does this answer apply to every ASUS model?+
No. It is scoped to UX5406 series. ASUS PC; full model code determines BIOS, GPU mode, USB-C video, charger and driver package.
What should I record before troubleshooting Bluetooth or pairing?+
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 Bluetooth, pairing. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Stop for swollen/hot accessories or damaged charging ports.
Answer for the exact device and software version shown above.