L120 PTO engagement?

the pto won't engage. With the key on, engine off, pto turns on & off with the pto switch, set on the seat and the pto turns off, get off the seat pto turns back on. Start engine set on seat turn pto on nothing happens, get off of seat pto try's to start but engine dies. Engine runs fine otherwise. I cleaned all the connectors, grounds etc.... I'm stumped, any help would greatly appreciated.....