just a black screan that got a bit lighter

I have a Galaxy Tab A7 that completly died and i plugged it in and let it charge for a few hours. Later on i tried turning it on and it was just a black screan that got a bit lighter for a second when i held the power button and then shut off again. I tried plugging it in a different spot and it was flashing the battery symbol on and off the battery simble is a circle with a lighting symbol inside, When i unplugged it the Tablet stopped flashing. My Tablet is not currently plugged in, does anybody know how to fix it?