Ray, I am afraid the list is long... Something, either on the engine side or the generator side is not setting the right conditions to allow the generator to run.
On the engine side the generator has to sense oil pressure or it will not latch the relay that controls fuel I think there are other conditions but the oil pressure sensor would be my lead candidate... On the generator side Frequency, voltage needs to be within normal operational parameters or latch relays that allow the engine to run will not be set.. Could be as simple as the brushes or brush block failure. Or the stator has failed.
JohnnyT