If the igniter doesn't glow, check the thermal fuse and the flame sensor. Be sure to un plug the dryer first, then disconnect the wires from the fuse or sensor before testing resistance. They are 120 volts with dryer off. They will either be open, or good. If the fuse is bad, you must look for obstructions in the exhaust venting that caused the overheat condition or it may happen again.

If it does glow and doesn't light, it is probably that the gas coils are weak. If new install then make sure the gas valve is turned on.