Piggybacking here to say that even if the city water is working, there might be a frozen water loop in your house if it’s near an exterior wall. I woke up in the middle of the night to no heat, and this was the issue. Had to thaw my pipes with heaters/heated blankets to get the furnace to kick on again. ALSO, have you tried the reset switch on your burner? That can sometimes get it to kick back on.