My thermostat in one room won't turn on the gas furance or start the air conditioner. I have switched the units around to different areas in the house ( I have 4 units) and they all seem to work except none work on this one room.Cleaned the wires and do not see any loose wires. Anyone have an idea ?

Sounds like maybe you have a disconnected or broken tstat wire that's not sending a signal, could be on the other end at your furnace