Here is a site with some picture, there is one with a junction box that has a lot of wire and screws to tighten.
https://www.etrailer.com/Camper-Jack...nt=30%20-%2060
This page also has a link to instruction on installation, that has a schematic.
The trailer is only supplying power, so the problem has to be in the jack (famous last words)
hope this helps.