Might have oil residue in lines causing restriction in line to gas control, tho if it lights manually, sounds more like an igniter problem. Maybe the spark isn't strong enough--is the gap correct?
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired