How do I know whats wrong?
I have two of the same apple displays connected to my laptop. It used to all work but one stopped working. I tried trouble shooting. All the ports in the back are working. When I go to display in system pref. it show all three screens. I have even hooked up the bad one to my comp and then plugged the good display into the bad one and the good display works fine. Do you think it is the actual screen or could it be simple like the cable?