Nest Themostat has been working well for the past 2 years. I have two zones, and two thermostats. One of them gave me an error message about not being able to detect a common c wire. Now this thermosat is no longer online and operating the AC unit. The Common C wire appears to be connected when I removed the thermostat. I have had no issues since I installed the thermostat. Any suggestions of where else I can check?
