I had the same problem last winter. The furnace would start up, the "purge fan" or whatever you call it came on, and then nothing. I had 3 techs look at it, and finally an older tech came and found the problem. The fresh air intake was plugged up right at the furnace by leaves it had sucked up from outside. There was a screen right where it enters the unit. They had installed it with an outside "breather tube" because my first plans for the remodel of the basement had the furnace enclosed in a closet, but I decided not to enclose it. I went ahead and busted out one of the air intake plugs on the side of the unit, and taped on a fine screen to keep dust out.
Last edited by reivertom; 11/27/21.
