Thanks for posting here in the Community forum, and I'm sorry to hear about the situation. I want to check if you are still in need of any help. If so, please answer the following:
Where are you located? From North America or Europe?
Did you try using the Help Center or troubleshooter before contacting support? If so, which steps have you tried already?
What is the make and model of the cooling and heating system, including the make and model for the, fan-coil or air-handler units?
Does your HVAC system use a multi-speed or variable speed fan?
Did you verify if Fan and Heating still work?
Did you turn off the power to your HVAC system?
Are the breakers turned on?
Did you recently experience a brownout or blackout?
Did you have any construction or maintenance work done on your home?
Thanks for the follow-up information, and I'm glad to hear that it has been sorted out. In this case, we could tell that you have a heat pump system instead of a conventional system. On the other hand, if you've lost your internet connection on your Nest app, kindly follow these steps:
Go to Settings > Reset > Account Connection.
If you've already set up the thermostat on the Nest app, kindly remove the thermostat from the app first before you set up its internet connection again.
If not yet, just go to Settings > Network to select your WiFi network name and connect it again.
Let us know if you have any other questions. We're happy to help.
