It may sound like a silly question but are you plugged into shore power or have a generator running. I am not trying to belittle anyone but we have had people that thought the 120 volt outlets ran off the batteries. Unless the vacuum is 12 volt, I do not have one so my knowledge is limited.
Goody Two Shoes and the Filthy Beast
2008 Chevy Silverado 2500HD
Duramax and Allison 6 speed
2012 Wildcat 282RKX
You can't make things idiot proof, you can only make them idiot resistant.