Steve,
If I remember right, there is a fuel solenoid valve that has to open at the generator. When you press the start button, there should be voltage on the solenoid valve. It should be on the incoming gas line, housed within the generator. You might try checking the voltage on that valve, and if voltage is present while cranking, you could also try tapping on that lightly with a small hammer, in case the valve is stuck. Beyond that, there is a large diaphram regulator mounted on top of the generator that sometimes gets clogged with very viscous oil, that can come from a contaminated batch of propane. Becuase the generator uses a liquid gas delivery, the oil can be carried along with it. I had to pull mine apart and clean it, but there is not too much user friendly stuff to work on in that fuel delivery system. As mentioned, there usually is a liquid propane valve of some kind, that needs to be open to supply the genset. It is at the tank. If you plan on pulling anything apart in the fuel system, be sure that the liquid propane supply valve is off, and whatever you take apart, check with a soap solution under pressure, after you put things back together, to be sure that there are no leaks.
later Ed