Do you have tools? Can you disconnect all of the wires except the two (red and white) that go from the converter to the battery? If so, I would do that. Then unplug the converter from the AC power and if you have a couple of fuses from your truck. 20 amp would work. Replace the fuses in the converter, then plug it back in and see if they hold.
But before you do that, let's try this first. Disconnect the red and white wires from the converter. Then replace the fuses in the converter and see if they hold. If they don't, there is something wrong in the converter. If they hold, then disconnect the wires mentioned above and only connect the wires to the battery. Make sure the converter is unplugged when you disconnect and reconnect any wiring.
It's 11:30 PM here, so I will sign off for now. Will check in on you in the AM.
If the fuses hold with only the battery connected to the converter and you can power the trailer with the generator, you may be able to get the battery charged up and we can go from there.
Knowledge: "A gift to be shared. A treasure to receive."