Here's a tip that I got from a copy-machine repairman.
When an electronic device goes on the fritz, we push a lot of buttons and switches trying to make it work. This can produce so much static electricity on the circuit boards that the poor machine is paralyzed and can't do anything.
Unplug the machine from the wall and let it sit for a while. With a computer, I would let it sit overnight. Then plug it in again and see what happens.
There have been times when this simple cure solved the problem. At other times, alas, it did not. However, it costs nothing, so why not try?