This worked for my VK810... my tablet was unresponsive "dead"
1. Hold the power button and the volume up/volume down button (directly in the middle/center of the volume +/-.... So right between the two! Not one or the other, middle so both!) for 20 seconds...
2. Keep holding the middle of volume+/- and power button and plug tablet into usb wall charger.
3. Release both buttons.
Hope this helps!