I'm in a 2019 384BR.
I know this is an older post, but I came across it when I had issues today. For what it's worth to anyone, I had a lot of rain today then the outside temp dropped. Turned on furnace and had similar issue--fan came on, furnace would kick on for 2-3 seconds and back off. Would repeat 2-3 times, then not come on at all unless you turned off the thermostat. Issue repeated itself. I took the exhaust panel off and there was a little bit of water ono the inside including at the bottom of the control board. Took a blow dryer to it and made sure everything was dried up. Turned the Furnace Heat back on and works just like it's supposed to.