I had this problem on a 2015 MacBook retina screen. The laptop took a fall (of about 4 ft) onto a concrete floor. That was last week, Tonight after a long day in in my backpack in the cold rain a big black band appeard on the side of the impact. I tried the screen massage technique, and it wokred so long as I held a finger there. Couldn't unscrew the back because f*ck Apple's prority tools. BUT I wedged my flat head precision screwdriver around the part of the screen that dips below the body (when the screen is open) and it seems to have reconnected. Works fine now! ( I did this 2 min ago, so I hope it stays.) No more trips out of the house in the cold for this one, that scared the sh*t out of me.