compressor fine one day, will not start next. what is the most common problem?
Hard to be specific with so little to go on.
Start by emptying the tank, then closing the tank drain.
Check to see if there is there power at the plug.
Try to start the CAP 2000 air compressor.
If it will not start with the tank empty, check to see if power is getting past the pressure switch to the motor circuit.
Post findings as a comment here.