I have a Macintosh Performa 200 and I’m trying to get it working again. It powers on normally and then it brings up the normal Mac OS screen but the mouse and keyboard don't work. Yesterday they were working fine but today the mouse will not move and the keyboard does nothing. I have plugged both directly into the computer but this doesn't help?
The Performa 200 has an ADB fuse soldered to the main board. From this picture of the PCB, it seems to be F2, located in the upper right corner between the DB19 connector for the external floppy and the 20-pin header for the internal one. This fuse sometimes breaks when ADB devices are plugged into or unplugged from a running system.
However, as Raffzahn suggested, you might accidentally plugged the keyboard and/or mouse into the Mini-DIN 8 modem or printer ports. This might have caused damage to the connectors or the peripherals.
I have plugged both directly into the computer but this doesn't help?
The Performa 200 is, AFAIR, a Classic II, thus using ADB. Mouse goes into Keyboard (either side) and the keyboard connects to the ADB plug on the Mac. That's the single, leftmost DIN plug, right between Audio In (to the left) and External Floppy (to the right).
From your description I assume you have pluged them into Printer and/or Modem which are two DIN located all the way to the right (between SCSI and Audio Out).