Replaced the air suspension compressor and both rear air bags, unit came on for a few seconds, shut off and never came back on again. I have checked fuses and relay, disconnected battery, cannot get compressor to come on, any suggestions?

 

I had the same problem, once, and it turned out to be a bad air compressor. Sent it back and they sent me a new one, which worked fine. Sometimes, new doesn't mean it can't be a bad unit.