Here is the content from my comment in the above link
I had a new boiler and nest learning thermostat installed yesterday and have had the same issue as many others - Nest working in Nest app but not showing on Google Home app.
I read lots of comments and saw the create new Home and transfer all item. This seemed a little long winded so I tried something slightly different which worked
I solved this issue by
Opening the Nest app and changing the room (I changed it to Attick as this was not yet used in Google Home app)
Checked it was still working in Nest app
Opened Google Home - Nest now appeared in Home app in Attick
Still in Google Home opened the Nest thermostat and selected settings and changed location from Attick to Living room.
All now working through Google Home app and with voice commands through Google mini speaker.
After this I went back to Nest app and changed location from Attick to living room.
IMHO everything had been set up correctly and should have worked correctly. I think that there is an issue with the labels for rooms conflicting whereby if you already have the room setup in Google Home it will not accept a second version of this room with the same name from the Nest app.
If you have had this issue and used the above information to solve your problem please take the time to comment or link to this information to help others solve this issue sooner.
