If you have the Dometic Single Zone LCD thermostat, E1 is a loss of communications with the control module. But I think that only applies to the air conditioner. With the thermostat set to HEAT, and FAN on AUTO, it shouldn't come into play. I don't think there's any intelligent feedback or error codes from the furnace to the thermostat.
First, make sure the thermostat didn't get bumped out of HEAT mode.
Second, either cut battery and shore power to force a reset of the thermostat, or pull the fuse for the thermostat.
If that doesn't resolve the problem, I would check the plug or wire connections at the thermostat. On a 2011, there may be 3 wires held to the board by screws. Make sure they're tight.