Factory reset isn't going to do much I'm afraid, of course you can always try.
Have you tried re-flashing the ROM? You'd need a fixed ROM for that and haven't been able to find that yet.
Check out the following links:
1)
[To see links please register here]
(I assume that it works about the same for your tablet)
2)
[To see links please register here]
3) Other
[To see links please register here]
you might want to check
I hope these resources can get you started and help you. Anyway seems the tablets have a whole shit load of problems. Nextbook tablet's seem to be pretty bad overall, with users being locked out of their device and other problems.
You're best bet might even be to try and get root access to the device so you can install your own Distro or reinstall the current one (if you can find an image).