What should I do with a tablet's black screen?

[AC Question]

Please help. My tablet's screen turns black whenever it is being charged. I can't turn it back on because the buttons (power and volume buttons) are broken/unresponsive. I tried to unplug it from the charger but the screen still remained black. I have an app named Gravity Screen that tuns off the screen if it's left idle but in this case, it's not working too when it's supposed to lock my device. This app unlocks my device and turns on the screen when it is pulled up in an upward motion but in this case, it left my phone's screen on with a black screen. I don't know how to turn it off since the buttons are not working at all.