dudu7; 360 cameras, reverse cam is blacked out?

I installed just my rear camera over the weekend and wired it one end up to the reverse light trigger, and the other into g5 (brown wire) on my dudu7. it triggers correctly and automatically goes into the rear view camera, but it's just black. i tested the other cameras, directly to the shorter harness at the headunit just to make sure it wasn't the wiring on the way to the trunk and all of them displayed black.

do i need to have the other 3 cameras for the rear camera (in the 360 configuration) for it to work or can it work stand-alone. i plan on installing the other 3 cameras over the next few weekends, but i don't want to install them if i have faulty cameras.

i did also use the front camera extension cause it wasn't long enough; but i bypassed that in testing.