I hope by now that you have found and corrected your issue, but a simple rule of thumb is: Check every connection that you can put a wrench on. A “High Ground” (loose connection) will cause more problems than you can shake a stick at, and some that won’t make any sense. The DC system is so dependent on solid connections, both positive and negative, but in most cases it is in the grounding circuit. It may be fine for a while, but eventually a loose connection will get a small amount of carbon (or dirt) between the points of connection and will over time will only get worse and worse, eventually stopping all flow of electricity.
Worse yet, as that connection gets worse, it can start to “Arc” which will increase the carbon buildup and then it will just “Snowball” uniting ie actually starts to burn.
For this reason RV owners should regularly inspect and tighten connections as needed. If you find one that is loose I recommend disconnecting the power then take the connection apart, clean all surfaces with a very fine sand paper Then clean all with 90% rubbing alcohol and re-assemble.