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Hello, these thermostats are *not always easily interchanged. there is most likely just a wiring error. Diagnosing the wide range of potential errors for a layman can be a lot more work than your skill sets might be up to.
There can also be complications at the units mother board.
Tell me which direction you are from the center of the nearest town or city if you would like be to get you a short list of well rated outfits.
The thermostats have to be selected for each type of system..If the power is not turned off when replacing or removing a thermostat, an electrical short can be created that blows the internal fuse on the printed circuit board or the 24 volt transformer entirely.
There are no reset buttons that address any of these things. There is also the issue of probable needed maintenance on the system that can be a complication
We can go from here as needed
Can you tell me what model on new thermostat is and model on your indoor and outdoor units?