I have 2 zones, one upstairs and one downstairs. The prog. Therms have been working well for 2 yrs, all of a sudden , the upstairs one does not fire the gas fired boiler when turned up, downstairs one working fine .no wires have been disturbed and I tried new batteries and a new thermostat to no avail, any suggestions??
mailman1
Ps I did try stripping the wires back even though the instructions say to just insert them and tighten the screw on the thermostat, it has a red and a white wire.

Jump red and white wire for the upstairs thermostat. If unit does not fire then the zone valve is not activating. Check control system with meter to find defective part and replace.