Chosen Solution
I did a battery replacement (the one where you remove everything in the computer) and when I restarted no video. I took the back off again and disconnected / reconnected the video connector. Started it back up and the display worked for about 5 minutes and the computer abruptly shut down. Now no video again. Using screen sharing I can see the MacBooPro’s desktop. Trying with a second monitor and there is no video. Looking at the screen on the shared desktop the under system information/Thunderbolt says that there is no device connected. Tried HDMI and no video. Any suggestions???
there is a small issue with mid 2012 retina, sounds like graphics card problem. but see if you disconnected any cables
