Nexia Thermostat not working

I am currently on my 2nd Nexia thermostat. Now I have no control of my Trane system that is just 2 yr. old. I have the extended warranty and now Trane is refusing to replace anymore parts. They are now saying my unit was not installed correctly.
Has anyone had any problems with this thermostat? This is my 3rd Trane unit in 23 yr. replaced by State Farm from a lightning strike. We started having problems with this new unit from the start.