I'm just guessing but I think you'll find the mice chewed through the wires that go from the control module to the pto solenoid. The pto light starts to flash because the computer isn't sensing any speed from the pto shaft then it will stop sending power to the solenoid. It could be a bad pto clutch, no pressure from the pump to the pto clutch, or something mechanical inside, but its most likely in the wiring or the solenoid went bad. I don't know where the solenoid is exactly on that model they are usually on back of the tractor somewhere. I think the controller for the pto is behind the seat or behind a panel on the back of the cab. If you test for power out of the controller ONLY use a multimeter otherwise you could damage the controller.