Dometic Furnace Won't Stay Lit

[mattf]

Having problems with the furnace in our 2019 3021RL. When the furnace is turned on the unit kicks on with the fan running, burner then fires up, but burner immediately shuts off while the fan still runs. This sequence just repeats itself until I shut the furnace off at the thermostat. When the furnace is turned on I'm getting one flash from the red LED light, then nothing else from the light. The exhaust tube is clear, there's no moisture that would affect the circuit board, sail switch was removed and is clean and moving freely, propane tanks are full, batteries fully charged. Any thoughts on what to check next?