My furnace won't start, it is an ICP NTC5100BFD. When the wall thermostat tells it to turn on, the inducer motor kicks on but it doesnt seem like it's igniting and the blower never turns on. The blower works fine independtly with the heat off. The intake filter from the cold air return was very dirty if that helps. I also checked the line to the pressure switch and it is clear. Kinda out of my element here, any advice would be appreciated. Thanks.