Since you indicate your belts are OK, next thing would be is to check for power being supplied to the PTO clutch.
First - with engine off - closely inspect the wire harness and connection to the PTO clutch itself - will be under main frame just above engine drive pulleys. Look for any damage. If OK and you are comfortable with using voltmeters, disconnect PTO harness, checking for 12 volts being supplied to PTO when PTO and ignition switches are turned on (engine stopped). If power is OK, most likely PTO itself has failed. If no power, check back thru circuit to isolate prob.
The type of PTO clutch on your machine is not adjustable - and is expensive to replace. Hopefully it will be a bad PTO switch or similar.
BTW, Before tearing into machine might be best to get it back to dealer to avoid voided warranty issues,