Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Make and model? Have you checked the seat switch and harness to it for a bad connection?
Check the park brake switch. It may be stuck, making the run circuit opem, which lets tractor think that brake is still on. As for relays, there are six relays , all alike, not identified as to each purpose. You could mark them, and then swap them to see if problem changes.
Ok, swap them and check that park brake switch!
The Deere link I sent showed 6 relays.