Did you bypass the seat safety switch? Youve got a couple interlock switches, one could easily be frozen in the "vacant" position. The seat safety switch needs to see the seat is empty {open} then it wants to see you sit down {switch closed} if it doesnt see these two events, it wont disengage...
Looking for a servivce manual for the Hesston SL-10. AGCO sells parts and operator manual...but no service? I dont suppose the operator manual is going to have information about the hydraulic circuit? item location, identification and hose routing?