Unit is warm, compressor not running

My client said it was cold and twenty-four hours later it was warm. When I check on it I found the evap and condenser fans running but not the compressor. I checked the overload and it was good, and there was 120v present at overload, did not find any voltage between any of the three wires that go to black plug that makes up to compressor terminals -wires are black, blue and purple. I suspect the inverter PCB is failed and wondered what you thought? Thank you.