Atwood 8531-IV-DCLP tries to ignite but shuts off after 3 tries

[dralkyr]

It's worked fine until late this morning. Now I try to turn it on and the following happens:

1. The fan turns on
2. The ignition starts
3. The ignition continues and heat blows out of the exterior exhaust
4. The ignition and heat stop while the fan continues
5. Repeat 3 and 4 twice
6. Turns off

I'm so confused because it is getting power, the blower isn't a problem, it's getting propane, and it's even igniting. I don't even know where to start troubleshooting.
Luckily we have a Big Buddy heater, but I need our main furnace back up.