You can try a factory reset:
- Charge for at least an hour.
- Force a power off by holding the power switch in the off position for 20 seconds.
- Hold the light button down and turn it on.
- Release the light button when the screen changes.
Hopefully that will get it going again.
If it doesn't, you can open it and restore an image to the internal SD card. I have sent you a PM with the link in case you need to do this.