I don't have the fancy schmancy digital thermostat, so when mine errors I have no idea what caused it (although after having it for 10 years I have a pretty good idea). But if the air intake or the vent hole gets clogged, that will cause the flame to go out. If the glow pin atomizer screen gets dirty and clogged, same thing. If the blower motor is going bad it'll shut it down. The blower motor will last an average of 5000 hours, some go as quick 3000 goes, some last as long as 8000 hours.
As OVM noted, there is some annual maintenance that needs to be done. It's listed in the manual, but basically it's clean it out. The glow pin screen and fuel line screen needs replacement every year.The flame tube will need a removal and cleaning of the carbon every year (or, you can run it on kerosene for 25 minutes to clean that carbon out). If you take it apart you will need new gaskets. Also, inspect and clean, or replace as necessary the exhaust pipe.
Try and fire it up again a time or two and see if it works. Give Ray a call at Espar. He can tell you what the likely cause is. 2 or 3 weeks ago I had my blower motor replaced, and they cleaned it out and burned some kerosene in it for a while. Repairs & installs are done by Brian at his shop in New Boston, MI, off I-275 by the airport, Sibley Rd. Thermo King works on them, but it's really hit and miss on finding a mechanic that's truly knowledgeable and anal about Espar heaters. Brian, on the other hand, is the Andy Bittenbinder of Espar heaters.