Sounds like what I just went through but be careful, sometimes descriptions can be misleading.
I just went through something similar during hunting season. Of course it happened about 9pm after I went to bed but as I got up in the night to pee around midnight I thought it was WAY too cold in the camper.
I checked the thermostat and it indicated it was 43 degrees. OH POO something was definitely wrong!
So I checked the propane first. Tank felt heavy, regulator showed pressure, stove worked fine.
Then I went to the manual. It indicated 3 fault failures and what kind of failure the little Control Board LED flashes meant. LED flashes? Where the heck is that?! Not visible on the side of the furnace, I can tell you that.
I go outside to see if I had an access panel on the side of the camper to get to the furnace opening where that Control Board sits...nope, not gonna line up with any kind of luck I have!
1am I finally resign myself to the idea I wasn't going to fix it that night so off to bed I go. Of course turning off my brain was a hell of a struggle but I finally convinced myself "I'm not gonna fix it tonight and there's just not jack-squat I could do about it.".
Then just after 2am I heard the furnace blower kick on then shut back off when the gas didn't fire. I then remembered reading that there were 3 types of faults listed in my manual; 2 HARD faults and 1 SOFT fault. The HARD faults (gas related and Control Board failure related) would shut down and never try again but the SOFT fault was air flow related and would try again every hour.
At that point I sure slept better because I was most sure it was the infamous Sail Switch to go after. OMG was it freezing in there and the camper belly at 5am!!! Was 33 or 32, not sure which but that's nitpicking about 1 degree.
So I have a look at the furnace and I have one of the dreaded "Pull it out of the cabinet" installs. That sucks!! But I knew it was tackle it at home after a ruined elk hunt that took 8 years to get a tag for or "What the hell, might as well get started here and finish at home if I don't get anywhere.".
I got the furnace partially pulled out and try to run it. NOW I see the light (LED flashes)!!! Yep, 1 flash indicating some kind of "air flow" fault. Now where the heck is that Sail Switch?
The wiring diagram showed 3 BLUE wires going to it and what do you know, it's right there staring me in the face on the side of what I thought was a big electric motor.
I pull it out, manually active it and hear it faintly clicking. So I put it back in and the furnace works. I tested it a couple degrees at a time that morning as I warmed the camper up...it keeps on working every time for hours...then it fails to fire again. Damn....
So I pull it and check the switch by letting the "sail" fall against it's own weight. 4 out of 5 times it activates the switch but then it hangs. At this point I recall all those who've been down this path before me and remember to add a small drop of oil to the sail/plunger surface. I grab my low temp gun oil and add just 1 tiny drop to that surface and the sail/plunger works every time with no effort at all. And continued to work fine for the rest of the trip.
If you pull the sail switch it may seem if works super easily but don't be dumb like me, add a drop of lubricant the first time before putting it back together so you don't have to do it twice
Good luck,
Andy