DIAGNOSIS The control panel has likely "frozen," which happens occasionally after a failed update or a minor software glitch. It's not broken, just stuck.
FIX You need to do a full power cycle. 1) Turn the printer OFF using the physical button on the back. 2) Unplug the power cord from the wall outlet. 3) Wait 60 seconds—this lets all the internal capacitors drain. 4) Plug the power cord back in. 5) Turn the printer ON with the back button. Wait for it to fully start up; the screen should come back to life and be responsive.
IF THAT DIDN'T WORK If the screen is still dead after the power cycle, there's a slim chance it's a hardware fault. Try the power cycle one more time, making sure you unplug from the wall, not just turn it off.
HEADS UP Avoid using the front-panel power button (if yours has one) for this reset. Always use the main rocker switch on the back for a complete shutdown.