I tried to lower the temperature on the digital interface, but it is not responding. The air conditioning is not kicking on, although the set temperature (78) is the same as what is reading on the panel as the air temperature. I go through the steps of lowering the temperature control, but the digital readout doesn't respond.

Some one may have programed a minimum temperature setting in the thermostat, you will have to access the advanced setup and reprogram it .

Your thermostat also may have a reset button depending how advanced your digital thermostat is, if you have one it will be a little button you can push with a small screwdriver or a pen.