Why wont my nextbook 10 screen change from black to normal?

Notebook type computers are tough to fix, let alone diagnose. The first thing you can do is remove the battery. While the battery is out, clean and check it for defects and moisture on its surface. Then also while the battery is out, place the Notebook in an electric or gas oven, at the LOWEST temperature setting, and let it 'bake' for 2 hours or more. After the time has passed, remove the Notebook from the oven, and turn off the oven. Before reinstalling the battery, press any visible reset buttons, usually a pin hole to a switch below, or if lucky a nice red button, as doing so will clear the CMOS and reset the BIOS, also carefully clean any metal contacts (usually gold plated) and the area where the battery goes. Install the battery, and close and re-secure the hosing, so it looks like it did before you took out the battery. If it powers up at all, it will be free of any moisture that may have been causing your problems.