When you say "off" just no display? Are you sure it's not the monitor itself? We had the same monitor setup and replaced it through rvcams.com with an LED flat panel monitor. I bet a call to them would get you more help. They were extremely responsive to my questions.
If you can get to the back of the monitor easily I'd first try swapping out the cable location from the back to one of the working sides to see if you get a signal there. This is just to check if the issue lies in the monitor or the camera.
As a side note. I replaced the rear camera with a color camera when I replaced the monitor.