Tablet won't boot, android lying on his back?

I'm trying to refurbish a Samsung Tab 4, 7 inch model. When I press the power button, the Samsung screen appears for a few seconds, then a standing android flashes on, then a screen appears with the android lying on its back, its front door open and a red triangle with an exclamation point by the open door, Then the screen reverts back to the Samsung screen again and repeats (boot looping). Hope all that makes sense. I've tried to hard reset it by holding the home, up volume and power button at the same time, but that doesn't help. Any ideas on what is wrong and how to fix it would be greatly appreciated.