Your power out of the converter is "ok" but no DC from that or battery. So it is about the DC fuse panel not being connected to either battery or converter. Those connect with wires from each going to the set-screw lugs on the fuse panel. There can be lugs on the back of the panel not just on the front.
If you measured the converter output as being ok at the fuse panel but no DC, then suspect the fuse panel has lost its ground to the frame (sometimes shared with the 120v ground --the bare wire going from the shore cord by the "main" circuit breaker. However, that might mean no ground for the 120v either.
You had a frame ground issue at the battery bank that you fixed. Maybe the same thing only now it is the fuse panel's ground?