Now that is weird.
Depending on the stereo you have, the video switch connected to your cameras and turn-signal is either part of the stereo itself (Jensen JRV212t), or an independent video switch module, or part of your monitor if the camera display is independent of the stereo.
The power source for the cameras can also be from the stereo, monitor, or independently powered.
In all cases, the power for both cameras and switch would be 12VDC.
It is a mystery to me how the generator would be involved...
unless the cameras are powered by the coach batteries rather than the engine battery, and somehow the coach battery got disconnected. Make sure the coach battery is enabled (should be a switch near the door of your coach with a green LED).
Thor started re-wiring the stereo systems from the engine battery to coach battery a couple of years ago so that you could listen to the stereo when you were camping without risk of running down the vehicle battery.
Previously, the stereo was connected to the vehicle battery. I suppose there are advantages and disadvantages to either method.
Of course, this assumes that the cameras are using the same power source as the stereo system.
The only thing that works on a RV is the owner...