||Hi Butch, some of the most common possibilities. Hope it helps. Good luck
BURNER IGNITES BUT IGNITION SYSTEM “LOCKS OUT” AND TURNS BURNER OFF
Low gas pressure - Set pressure to a minimum of 11˝ W.C. with all appliances running.
Replace regulator if not obtainable.*
Exhaust blocked - Clean exhaust.
Electrodes out of adjustment - Adjust electrode according to furnace specifications.
Electrode defective- Replace electrode.
Circuit Board defective - Clean plug contacts. If still defective, replace. (Check on board tester when possible).
Flame sensor wire between electrode
and circuit board defective - Replace wire.