My house has 2 HVAC units (gas heat). House is 12 years old. The upstairs unit is having issues getting cold and last year I replaced a bad capacitor. Now the unit is not working. New filter. The breakers and switches are all reset. Fuse on circuit board inside of unit is good. The digital thermostat only shows the current room temp but no other digits show up is you turn the unit on. I can change from Auto to on for the fan and it works. Any ideas? I have already checked the basic connects in the circuit board and inside the thermostat.