Also check the thermocouple aka flame sensor. This little sensor simply checks for heat, and if it does not sense any tells the burner to shut off. When they go bad, they don't sense the heat, and they won't let the burner stay lit.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2018 Nissan Titan Midnight Ed.