1 Nest Connects to App, Other 1 Doesnt

[NestHelpNeeded]

2 Nest Thermostats for app. 18 months. 1 of them lost connection to the app and i cant control it remotely while the other one has remained fine.

I have tried the majority of the troubleshooting steps but please give me all of the advice possible so that the back of my office can be heated and cooled.

Thanks in advance to all

[Apop]

You, probably tried resetting already also make sure you’re device code is correct, use the IR code to set it up, good luck