The Owner's packat, or the manufacture, or a forum, ideally for your brand, should be able to tell you about a switch and/or fuse.
RV builders do some ugly work, agreed. The convention, if there is one, is this: An access cover that's bradded/stapled in place shouldn't have anything behind it that you need. A cover attached with screws, velcro, or clips...might.
From what Doug says, I'm thinking there in fact IS a safeguard switch and somebody flipped it. Nothing happened, so they left it, and the flip happened to be to OFF.
Otherwise, look around your battery area. Maybe the Black and Yellow originate there. Otherwise, around your Fuse Panel.