2004 F250 Diesel 6.0 trailer relay wiring diagram

Evening gents,

my buddy has a 2004 f250. He bought it used and never towed with it.
His father recently purchased a 5th wheel and has told him he's able to borrow it.

Fast forward, and I put my 7 pin tester in the hitch and there's no turn signals or brakes (flashers) coming out of it.
I'm getting 12volts for the battery connection and the clearance lites only. I've not tested the trailer brake controller - yet. At least I wanted to get the turn signals and brake lights working.

I've chased the wiring to the fuse block under the dash, and the fuses are good.

I put a phone toner on one of the wires and found there's a trailer relay box under the hood. In it there are 4 relays and one 10 amp fuse - but there are three spots for fuses. The manual doesn't say anything about the wiring in the trailer fuse relay box.

Does anybody know anything about the wiring in this fuse box?
It may be the relays in the fuse box are shot, but without being able to chase the signals from the fuse box inside to the relays, I'm shooting in the dark.

Any help would be very greatly appreciated.

Thanks so much!

Josh