Hi there and thanks for reaching our community. I'm sorry to hear about your issue, but I'm here to help you out. In order to document your inquiry better, please answer the following questions:
How long has your thermostat been installed for?
Did the issue happen during the installation?
Is there any error on the Nest thermostat display?
Have you had any power cuts recently?
Have you had any work done on your electrical or heating systems recently?
If yes, was the power properly restored at the fuse board after work was done?
How many zones are present in the setup?
