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Make sure there is power to the unit that sits outside, if there is power, then turn it off, wait 5 minutes than turn it back on.
Make sure the batteries in the remote or new... and... correctly installed. If they are, remove them, place them into the remote backwards, for 5 minutes, then remove and replace them properly.
Beyond that these are entirely complex systems with several micro computers on board with very thinly distributed dealers and service capability in the US... tell me which direction you are from the center of the nearest town or city and I will see if I can find anyone in the area.
OR.. if you have a multi meter and set of refrigeration service gauges I can coach you on a diagnosis.
We can go from there.
If you can give me the model number on the outside unit I can look it up, or you can examine the wall unit inside for a flap that covers a control bar and try that. Let me know what you can discover, we can go from there.