No 12 V power at all W/O shore line or generator

I have sort of the same problem except that unless I'm hooked to shore power or running the generator the only 12 volt I have is to my steps. all other 12 volt systems shut off as soon as you shut down the generator or unhook from shore power. Also the coach batteries are relatively new. Any suggestions? I have a 1997 Damon Intruder with two 12 volt coach batteries.