I was just using it and I let the screen go off and now it will not do anything. I tried plugging it into a computer. It won't turn on or off. The battery was not low.
Typically, you still follow the traditional steps which does let you charge it for at least 30 minutes just to be sure the battery indication wasn't stuck at an incorrect reading:
If none of the steps there work, you'll need to take it in for hardware service or a replacement.