christieP.....I'm not sure how the 110 circuit interacts with the 12 volt circuit. I may be way wrong, but you might not be getting 12 volts to the circuit board, but when you turn it to AC, it may be supplying the voltage you need. I would check the voltage (12 volt) side and make sure your connections are good. Pull the 12 volt connections off and stick them back on. This is usually enough to clean them if they're dirty. Make sure your batteries are good and supplying 12 volts. Also pull the connector off to the igniter and reinstall.
Don & Mary
2014 Newmar Dutch Star - All Electric - 450 ISL
2016 GMC Canyon 4WD Crew Cab