Can not link tried it all...no vision either

[phantomike]

I have a P3 pro that I got from a friend it does not have a camera or a gimbal and it was in a crash. It looks in tact and everything seems to work correctly but I can not link a controller to it. I have tried to change out the board where the linking button is but that didn't help. DJI tells me that if I don't have a gimbal and a camera that it wont fly. Crazy is that true? I have another one that is being worked on so I borrowed the gimbal and camera from it. Hooked it up and tried to update the firmware with no luck tried to link no luck tried to remove the hood and exchange with another one no luck. visual inspection of circuit board and all cables seems to be fine. but the bird will not respond camera works on the other pro but not on this one but it won't link and I don't know what firmware is in it. Any help is appreciated