Take the camera off. Disconnect the wiring and tape it down so as not to loose it in the rear cap. Take the monitor out and plug the camera straight into the monitor. If it works you have a wiring harness or connection problem. I have extra monitor and camera for testing a system with to determine which is bad.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7