Did the same thing with Gateway laptop NE56R48u. Left it off for 3 days. Tried to power up while plugged into outlet. Nothing after several hours and trying several key combinations to restart, etc. Nothing. Shut down, unplugged, waited a few hours. Put on rubber soled shoes and opened up back hoping to find something loose, took out battery, then reseated. Still no luck.
After a few days, tried it again and nothing happened for awhile. Then Boot Manager popped up. Screen said:
Boot. Option. Menu
“Up arrow” and “down arrow” to change option.
ENTER to select an option
Then the rest of the screen is blank...no options to choose.
Nothing on keyboard seems to work.