Apparently there is some other wiring issued caused from the drain out of the battery. A main fuse somewhere other than the fuse box, that I can not locate.
Make sure the emergency break away lanyard has not pulled on the break away pin. The pin can still be inside the plastic enclosure and the contacts inside, connected. The emergency brake system is usually wired directly to the battery.
A powered hitch jack and slides should have their own fuses, too. Check for an inline fuse holder on the jack wires, it is typically on the (+) positive polarity wire and will be wired directly to the battery.
Another reason that no charge current is able to reach the battery may be that an in-line fuse or circuit breaker has failed. There should be this circuit protection within a few feet of the battery. Sometimes, it will be in a plastic enclosure, mounted on the frame.
If the battery terminals have ever been miswired/shorted and the onboard converter powered at the same time, a reverse polarity fuse may have been opened at the converter. These fuses are sometimes on the back side of the converter and not visible from the front.
All of these issues are easily diagnosed with the use of a hand-held meter. Do you have a meter or a 12V test light?