Why will my car blow heat but not cold air?

Last November I had a camera installed and new radio. We took the car in because we thought the A/C wasn’t working. 2 different mechanics said all the functions of the A/C was working fine but that a connection form the new camera and radio was what was messing it up because it was missing some parts. Okay, so we had the radio parts ordered that would make it function and in theory the A/C should be working. The radio and camera now have more functions than ever before, but still no A/C. Heat will blow though the vents but not the AC. What could all these mechanics be missing. Oh, and its a Jeep Cherokee 2016 model. Oh, one of the mechanics said he could make the A/C blow though the bottom vents but for some reason not the dash board vents. Why would that work?