I just found this video troubleshooting and repairing a gas-valve problem. It's on a more current Atwood (now Dometic) furnace but the principles are the same. It brings us back to the lack-of-propane issue... one of the possible problems with WillTheThri11's furnace.
I've thought this an unlikely cause of a furnace not running, particularly when there's good LPG pressure at the stove and the gas-valve solenoid can be heard opening and closing. But Darren suggests the smell test is a strong indicator of whether the valve is working or not. And it provides good info on bench-testing the valve and replacing the (dual) solenoids.
Also: (I should have done this earlier) - Here's a link to the Atwood Furnace Training Manual 2015 for model info, sequence of operations, component identification, troubleshooting charts, etc.