Did you replace the belt yourself?
You can check the seat switch easily by raising it up and making sure it's connected well, wiggle it some to seat it properly.
Make sure the battery cables are connected properly and fuses in tact. If a shop changed the belt they may have a safety protocol of removing a battery cable or etc.
Make sure PTO switch is off, your parking brake is set, control bars in neutral, and your in the seat. Try it again. Report back, if you get nothing, not even a click.