It may be obvious, but.... (Assuming a petrol boiler).... boiler plugged in? (I knocked my outside freezer plug lose last year while working in that room, and did not notice it till I smelled bad meat. Lost 100 lbs of moose, halibut, and some domestic stuff. Stink happens.) If so, hit the reset button on the boiler. Sometimes FM happens, too. Out of fuel? (Deliveries don't happen, and people steal fuel.) Water in the fuel line? (Check fuel filter.) Loose wires anywhere? Poke around and maybe you'll see something obvious.... I hope. I hate it when boilers go dead.