Nest Learning Thermostat (4th gen) is offline or unavailable

Look at the screen. The Learning Thermostat (4th gen) has a 2.7-inch circular display at 600 x 600 pixels; the Nest Thermostat has a 2.4-inch rectangular 240 x 320 panel behind a mirrored lens. That is the fastest reliable check, and it matters because the two have genuinely different wiring capabilities.

No — it uses a built-in rechargeable lithium battery charged from the HVAC wiring, not the 2 AAA alkaline cells used by the Nest Thermostat. So a low-power symptom on this model is a wiring or charging investigation, and swapping batteries is not a step that exists here.

Google states it is designed to work with or without one, using its Power Sharing technology, and that in fewer than 1% of cases a C wire or a Nest Power Connector may be needed to guarantee sufficient power in all conditions. So the answer is normally no, with a small and specifically acknowledged exception.

Up to 3 stages of heating (W1, W2, W3) and 3 of cooling (Y1, Y2, Y3), plus heat pump up to 3 stages with 1 or 2 stages of auxiliary or emergency heat. That is substantially more than the Nest Thermostat, which handles one stage of each plus a second stage of either — the main reason to choose this model on a complex system.

Watch the connector limits. Google states the * connector accepts only ONE of W3, Y3, G3, E, HUM or DEHUM, and the AQ+/AQ- connectors accept only Y3 or 1-wire or 2-wire VENT, HUM or DEHUM. On a system needing several of those, this constraint decides the installation before anything else.

Yes — 802.11n on both 2.4 GHz and 5 GHz.

It uses a Soli radar sensor for Motion Sense rather than a passive infrared detector. Radar responds differently to approach and to movement behind objects, which is why its presence behaviour does not match the plain motion sensor in the Nest Thermostat.

At the router or the hub, not at any device. Simultaneous failure across unrelated hardware is the signature of a shared dependency, and re-adding devices one by one before that dependency is fixed is work you will have to repeat.

It rules out the router, the internet connection and the provider — all of which would take the others with them. What remains is that device's own power, its own radio path, and its own account state.

That interval is the clue. A drop that recurs on a roughly fixed schedule usually tracks the router's DHCP lease. A reservation for the device's MAC address at the router removes it permanently, where rebooting only resets the clock.

Both, in sequence. Marginal signal degrades first — slower live view, late notifications, missed events — and only then drops out. A device that went straight from perfect to absent is more likely a power or credential problem than a signal one.

Because they still hold the old network's name and password, and nothing can tell them otherwise. Setting the new router to the old network name and password is often faster than re-adding every device, and is worth doing before the first re-add.

Then the local link is probably fine and the break is further along — between the router and the provider, or at the provider itself. Check the provider's status page and the router's internet connection before doing anything to the device.

Not as a first step, and not during a provider outage. A reset discards local settings and, on a shared device, can discard other people's access. Establish what is actually broken first — reset is a recovery action, not a diagnostic one.

No, and it is rarely necessary. Deleting a home or hub destroys every automation, permission and share attached to it. Remove and re-add the single failed accessory instead.

Router firmware updates can turn on band steering, IoT client isolation or DNS filtering that was previously off. Compare the current settings against the defaults for those three specifically — a device that worked for a year and stopped on an update date is describing a router change, not a device failure.

Router first, fully up, then the hub, fully up, then accessories. Restarting everything simultaneously produces address conflicts and rejoin storms that look exactly like the original fault, which is how a five-minute check turns into an afternoon.

Give the router several minutes to finish handing out addresses, and battery devices longer still — several report on a duty cycle and will not check in immediately. Judging at thirty seconds produces false failures and unnecessary resets.

It can. Consumer routers have finite client tables, and a household with dozens of connected devices can exceed one. The symptom is that a device drops whenever a new one joins, which reads as random until the pattern is spotted.

That is a useful, specific result: the device joined the local network successfully, so credentials, band and signal are all fine. The break is between the router and the provider — DNS filtering, a firewall rule, or the provider's own service.

No. It is scoped to GA05551. Google Nest/Home device; Matter/Thread role, wired/battery power, subscription and Google Home migration vary.

Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.

A reset can erase accounts, networks, maps, schedules or preferences without distinguishing offline, unavailable. The ordered checks preserve that evidence.

Protect security devices and avoid deleting the entire home for one offline accessory.