Try plugging the device into a computer, it should power up. The next thing you need to do is to disconnect it by clicking on "stop USB safely. Plug in the power adapter and charge the Nextbook without turning it off, leave it on when charging. Good luck!
Try hitting the control, alt and delete button at the same time and it should restart. I've had problems lately with mine staying connected to wireless but not sure why. You might also want to defrag your netbook. See if that helps.
I had the same issue here's what I did to fix it. I finally got it turned on I backed up everything on a SD card I did a factory reset but I find that the screen timeout feature played a part so I turned that off. It isn't perfect but it's working.