Diagnosis
A software glitch has locked up the machine's computer. This sometimes happens after a power fluctuation or an interrupted cycle.
How to Fix It
Perform a hard reset.
1. Unplug the machine from the wall outlet.
2. Wait a full 60 seconds for all residual power to drain from the capacitors.
3. While it's unplugged, press and hold the main power button (if it's a physical button) for 10 seconds.
4. Plug the machine back in and turn it on normally.
If That Didn't Work
The screen itself might have failed. As a last resort, you can try a factory reset via the hidden service menu, but this erases all your profiles. Consult for the button sequence to enter that menu.
Heads Up
Avoid turning the machine off at the wall regularly. Use the main power button. Frequent hard power cuts can corrupt the software.