Does your plug have two wire bands on each side of it? They don't seat right in the opening causing resistance.
This type of plug was the older version and actually had a recall on it.
Mine would not seat properly leading one to believe something was wrong with the system itself when it wouldn't function when actually it was just the plug not seating right with those two stupid wire bands.
I just had the RV mobile repair guy come out and he cut the old one off and put a new cig plug on it. Never had a problem after that.