This is for anyone having the problem stated at the top of this thread:
I had the same issue. I hooked up the reverse camera (using the reverse light for power, so only turns on when in reverse). I do CCTV systems for work, so I have a small battery-operated test monitor. I put the car in reverse and verified that I got a picture on the video wire. I connected the video wire to the proper reverse cam input RCA, and then I hooked the trigger wire to the purple/white wire on the harness going into my X930BT. I nearly went crazy because everyting was connected to spec, but the camera did not