The top fuse is labeled Batt+. Again it looks like they use black wires for the positive. Yikes!
First thing to do is to check the voltage at the black wire at that fuse. Check between there and ground. Then pull the fuse and check between the other side of the fuse holder and ground. If the second reading is higher than 12.4v, then the fuse is blown. Confirm this by checking the resistance across the fuse with your meter.
Hopefully that is it. You'll just need a new fuse.
However, I didn't see a converter in your pictures.
