The junction box has no power to the plug

Help me understand what junction box you are looking at and where you are not getting power.

Are you looking for power back at the trailer tow plug?

If so, we need to check the fuse in the under-hood box that is the 40-amp fuse labeled stud 1.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If you have power here, then we should have power to the connector. If you don't then you have ground issue or a wiring issue.

Let's start with the details as to where you are not getting power and then we can go from there just to be sure we are on the same page.

Thanks