Microscopic propane loving spiders.
You think I'm joking... but there are tiny tiny spiders that get into the burners in the water heater, furnace and refrigerator. The aperture for the propane burner is small, and the parts are easily damaged so don't go poking around with anything metal. A soft camel hair brush (steal it from your kids watercolor set or the wife's makeup) can brush out the aperture letting the propane flow properly. Compressed air can work too, but don't overdo it.
Oh yeah... Do the battery thing too. After 2 years if the batteries were left in the A/S over the winter when it was in storage they could be toast. First check and refill the water, then put a charger on them. If the charge doesn't hold, replace. NOTE - the newer Airstreams have phantom draws on the batteries out the wahzoo. The face plate on the sound system is significant. also any little sensor lights, etc. The water heater and furnace and thermostat, and propane alarm are a few of the others.
One last D'oh!
Right by the door, there is a switch to flip when you're storing the RV so that the batteries won't drain as fast. Did you perhaps hit it by mistake? Do not flip the "storage" button when you're using or towing the unit... brake lights, e/r breakaway switch... reefer keeping your food cold on propane.