Heil furnace Won't work.
If the igniter is lit and it is still not firing up, the next thing i would look at would be the thermocouple. This is a thin piece of copper tubbing attached to the igniter assembly, which detects heat from the igniter, if it can not detect that the igniter is lit, it will not open the gas valve-hence no heat! These are pretty cheap and tend to go quite often, it could be other things, but this is prob the most common.
Also remove igniter and clean with a metal brush or fine sand paper. If the flame has a yellow tip-it needs to be cleaned.