NOTE: the purpose of this post is to suggest POSSIBLE issues and options.
On my coach there is a disconnect, most all (of not all) motor homes have them, I won't bother you with where mine is since you already looked there.
BUT. In addition to this switch, the diagrams for the battery control center installed in my coach call for a pair of 30 amp PUSH TO RESET circuit breakers in the bottom of the box,, You have to push in very very hard on these to reset.
I do not have those either.. I have a self resetting thermal breaker next to the box.
Some RV's have fuses or "Stand alone" breakers (like mine some self resetting some push button to reset)
And finally we have the ever popular bad connection.
There is more but that is more specific to my coach than yours.
IF you have an AUX battery switch.. that is your disconnect control, the actual disconnect may be elsewhere.