My heatilator intellifire was installed when we built our home 2 years ago. Upon first use of its 3rd season, it won't light! We've tried a new controller, nothing changed. The ignitor sparks when the wall switch is flipped. We've tried and read a lot of DIY fixes. No one cam service it until after xmas, and that's still a $150 service call alone. The model is ndv6236i. Any advice?