Black screen and unresponsive when I turn on any camera app.

I have an s4 verizon 16gb. Whenever i open the default or any downloaded camera app it shows a black screen. When i click to switch to front facing camera it is unresponsive. I have a spart parts s4 (busted glass). Whats the problem so i know which parts to switch out. The camaera not letting me try and use even the front facing camaera makes me wonder if its the camera at all.... It also has a 2 pixel wide pink line down the screen. It was refurbished by asurion. Any ideas so i can begin fixing instead of just trial and error? Thanks!