I have found the Cust Svc at Power tech to be helpful.
If you down load a manual for a newer 7.0 generator, you find trouble shooting steps for the Kubota engine and the Power Generation system.
Those steps have saved my bacon several times.
If you measure 12v at the back of the on-board switch then your problem could be either with the engine or the power generation system.
If no 12v at back of switch you could have a broken wire or failed fuse leading to the switch.
The engine will shut down, or not start, if the shut down solenoid is not working, if fuel in the tank is below 25% full, if the oil is low, if the coolant is low.
I seem to remember that the engine will start but not run when the power generation system is the problem.
There are three relays behind the switch. Buy a new one and switch it among the three to see if replacement helps. I fixed my 7.0 in that manner one time.
I also had my 20 yr old starter motor lock up once.
Also had the power generation system problem, but had it fixed by a generator shop for about $300.