If the mouse on your Amiga 2000 suddenly quits working, check for +5V missing on the mouse/joystick ports (pin 7).
If you don't find +5V on pin 7, check for one of these fuses (which happens to not look like a fuse) on the board up near the joystick ports, and if you find one, check it for continuity. It's quite possible that it's blown and will need te be replaced.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko