Heating intermittent on nest thermostat

[Swindon1]

I have new nest thermostat. The first day the heating fired up no problem. Next two days heating would not respond. Yesterday it was responding and today not responding again. I cannot understand why it sometimes works, sometimes doesn’t?

[zoeuvre]

Hi Swindon1, 

Uh-oh! I'm sorry to hear that your heat works intermittently. Let's see what's going on. A few questions:

• Are you located in North America or Europe? 
• What type of Nest Thermostat do you have? 
• Is the Nest Thermostat newly installed?
• Did you use the Compatibility Checker tool to confirm the thermostat's compatibility. 
• Does the thermostat screen indicate that it’s actively calling for heating? 
• What type of furnace do you have? (gas, electric, etc.)
• When did heating last work? 
• Did heating ever work with the Nest thermostat? 
• Did the heating work with the previous thermostat? 
• Did you turn off the power to the HVAC system? 
• Did you recently turn off any breakers?
• Have you recently experienced a brownout or blackout? 
• Is there a light switch near the heater that controls an outlet? 
• Did you select the correct fuel type? 
• Do the LED lights blink on the HVAC control board? If yes, locate the light. 
• When was the last time you changed the furnace's air filter? 
• Have you experienced extremely cold weather lately?
• Is this the first notable temperature drop of the year in the area?
• Is there any error code visible on the thermostat or on the app? 

I'll look forward to your response. 

Best,

Zoe