Are you visually confirming that it isn't lighting? Majority of the time the problem is with the flame verification system,
and not the flame/ignition itself.
If you are not getting _any_ flame, did you replace the spark plug? Insulation can wear over time and short to the body.
Also, did you use the correct wire for replacement? If you've ever worked on a vehicles ignition system it's damn near the same.
If you are getting any flame but it is not staying lit, check the flame rod (assuming this vintage uses one) and clean it or better yet replace it,
and check wire connections/continuity. This signal is in the microamp range so any loss can null it.