3 axle break controller issues

Great input - I agree the 2nd controller makes sense now. I still don’t know why the truck is deciding to not send any voltage....not the best default if you ask me.

I tied into the 5th wheel wiring in the front compartment before it went into the under belly and then ran a new 7wire all the way to the back of the 5th that the ATV trailer then plugs into.

Thanks for the input!