Hey npetru,
Sorry for the delay but thanks for reaching out to the Google Nest Community.
What type of Nest thermostat is this? Have you ensured that all switches on your HVAC system are powered on? If yes, could you check if your Nest Power Connector is being recognized by your thermostat? To do this, go to Settings > Equipment > Wiring info. If it appears grey, try the suggested troubleshooting steps here: https://bit.ly/3GzjC6x
Let me know how it goes.
Best,
Melba
