Hello @madaerodog
no, afaik the display doesn't have any internal memory that would need erasing.
I am afraid something got broken or dislodged within your M5Core2, but since you wrote you won't be able to return it, the only thing that comes to mind you could try is to remove the small little white board labelled CORE 2, unscrew the bottom and disconnect the battery. Then try w/o battery and only with USB plugged in.
Note: be careful when removing the bottom as the battery is taped to the bottom but plugged into the main board.
Good luck!
Felix