DIAGNOSIS The generator is getting vapor from the propane tank, but not enough fuel pressure or volume to sustain itself. The most common culprit is the regulator on the propane hose assembly, or the fuel selector valve not being fully in the propane position.
FIX First, ensure the propane tank valve is fully open. Then, check that the fuel selector knob on the generator's control panel is turned fully to the "Propane" position—it can feel stiff and might not be fully engaged. Next, inspect the hose and regulator for kinks. Finally, try a different, full propane tank to rule out a tank-side issue.
IF THAT DIDN'T WORK The internal demand regulator (mounted on the generator frame, where the hose connects) might have a stuck diaphragm or be blocked. You can try tapping it gently with a screwdriver handle to free it. If that fails, it likely needs replacement.
HEADS UP Always perform the fuel switch with the engine OFF. And when you switch back to gasoline, you need to run the carburetor dry of propane by letting it die on the propane setting before switching the knob, otherwise you'll have a hard time starting on gas.