Follow the wires from the PTP clutch on the end of the output shaft back up to the switch.
They take a beating and oft get work through by a belt if not secured out of the way.
They also get snagged if rough cutting undergrowth.
They also corrode.
There might also be a separate fuse for it.
PTO switches do go bad occasionally .
However I have bought 4 in 3 years because I was sure the switch was bad.
All of them are sitting in the electric parts bin.
