Google Nest Community

Check the furnace.  That is most likely the problem. 

That means that your heater is not working.  The Nest thermostat is.

Have the furnace checked. I had the same issue but it wasn't the Thermostat, it was the furnace.

Call a HVAC service company that have a person familiar with Nest. I had the same issue and found out that the NEST was fine. My Heater needed servicing. Now everything is good again.

I just reset the schedule using the wall mounted Nest, and the furnace turned on for 2 minutes, then turned off again for a minute, then turned back on (as is running now) I am hoping it continues to work as the night temperatures the next 7 days are...