I have an A.O. Smith H2O tank with a power blower vented out the foundation of the house. All the thermostat controls are electronic and the entire system was new in 2007 when we built our house. All of a sudden the led panel is lit up indicating system is in lockout mode? Possible solutions in troubleshooting were 1. Gas supply off or low(NO) 2. Hot surface ignitor out of place (NO) 3. Low voltage to tank (? All of a sudden? ) 4. Electric polarity is incorrect?? (All of a sudden? ). Any suggestions?