Help with trailer lights question

[Parnell]

Need help determine the issue. I have 2 trucks, a hunting/mowing/farm truck 2004 Chevy. The other is 2013 Chevy I pull the boat to lake with. I recently purchased a cargo box trailer. I pulled it home with the 2013 Chevy and the lights on the trailer worked. When I hooked it up to my 2004 mowing truck no lights work. So I hooked my mowing trailer up to the 2004 all lights worked. What’s the issue on the cargo box trailer and my 2004
Chevy truck?

hope makes sense, and I can get a starting point to the issue. Thanks in advance.

[CJ1]

First thing to do if no lights work at all on the older truck is to be sure the ground through the plug is working. Cj

[Parnell]

Found issue was ground.