Hi, just recently purchased a 2022 Focus STline Vignale estate with sync 4 with no reverse camera. It needed a replacement tailgate so the doner came from a 2023 ST that had a camera already fitted. Checking my wiring loom against the ST and they were identical. Had a chap round who went into the system and enabled everything that was disabled. When you now put it in reverse the screen changes to a black screen for a few seconds then a message appears saying camera unavailable. So my question is, is there another module that this needs to be plugged into before it gets to the infotainment screen ? Or is it perhaps not plugged into before? If I’m missing something I’d be very grateful for any advice. 
Thank you 

I know this is quite old so you will have possibly got the answer already, but there is an additional parking camera module for factory cameras that your car doesn't have, what I have done in the past is buy a camera boot latch button, ran the wires to the radio and pinned in a RCA to pins adapter into the radio plug

It doesn't work for you because your car doesn't have the necessary wiring, the connector you see that has the gate command, sound for the lock and lights, but not for image. I have an MK4 with Sync3 with the same case, a Titanium without a rear camera. I have bought in AliExpress a proton blanket with camera, and it comes with an adapter to connect the yellow video rca of any camera (it can be done without the adapter) but in short, the problem is the wiring you lack . I don't know what wiring would be missing in your case without resorting to an AliExpress kit.