The bad news is that these types of problems are not rig specific. This occurs on many brands and the popular brands of furnaces in all these rigs, too.
You've mentioned the most obvious but it sure seems like the propane is not getting through somehow. If you can hear the igniter clicking, then it might be getting enough propane to turn on.
Do other propane appliances work okay? Have you tried a full tank versus a not to full tank? These will help identify a pressure problem.
Other things that can go bad are the control board, that tells the propane to flow so that the ignitor has something to ignite.
This are not all the answers. Hopefully others may have ideas to add.