Propane does flow fine…. Blower comes on and I hear 3 clicks runs through cycle twice and doesn’t come back on.Bad ignitor, bad ignitor-burner distance, bad burner, bad orifice, orifice full of bug carcasses, bad board, of course assuming propane flow is good. Does it try to light and go out, or not try.
Maybe third time will be the charm?If you would post the make & model of your furnace we could then look at the service manual to give more specific information. Since you seem to be getting an attempt to ignite, that would indicate that the sail switch is being actuated by the air movement, as it should be. The next thing is to use a multimeter to see if the propane valve is getting 12V power and also to check for an open winding on the valve solenoid. If you can, try to watch the burner area as someone else turns the thermostat up to call for heat and see if you can see the flame burning before it shuts off.
You said that the propane "does flow fine." How did you determine that?