Why is my FaceTime Camera not working?

So I got an iCloud locked iPhone 5 to swap my iPhone 5's motherboard with because my housing and screen were in horrible condition, I got it all back together and everything works, except the front FaceTime camera. It's connected, I did a DFU restore, and the Proximity sensor and Ear speaker work fine. It was doing the same thing before with my old iPhone parts, but I thought maybe that one was faulty so this would help. It hasn't. Is it a motherboard issue? Or something else an easy-peasy fix could do? Please help