@Wayne-TP 

Reset the thermostat I was having issues with "low battery" and "fault". So back to Factory settings and added back in on the Tapo app.

It initially refused to install until I swapped my phone over to the Deco IoT network the thermostats are on. 

It then installed, but refused to connect to the T310. I had to try several times to do it, eventually it connected.

It then asked to install the new Firmware (2.9.0) as it was still on 2.8.0.

Firmware downloaded, installed and restarted. 

Reports its on 2.8.0 and there is new firmware available.......ad infinitum.......

Initially reported correct room temperature. 

2 minutes later, it is now showing 16 degrees again.

I can't upload photos of anything as it seems TP-Link forums won't accept/upload photos from my Mac's Safari browser.

@Wayne-TP 

I guess I'm talking to myself here but one last message.

All thermostats are now stuck at 16 degrees. All thermostats think the room temperature is 16 degrees.

I've removed all the external sensors T310 and T315. No difference.

I might just as well have manual valve on my radiators.

  @Wayne-TP too late. I removed all the thermostats and returned them to Amazon who are in the process of refunding me.

Feel free to close the ticket, you lost a customer, permanently.