I am not sure, hence question, my son got a brand new p3 yesterday that had the camera swapped and its refusing to activate. He did get some text from DJI which not sure what this is about also a short video.With the p2V+ you just plug it in and it's ready to run.
Maybe the P3 is the same?
Yep linking or sme say binding procedure. Set up proper communications between to camera/gimbal and the controller to send video back FPV.
Also if camera was swapped with a different model (Advanced or Professional) check that Phantom software matches the camera type, load the correct software from DJI site if different.