trailer not braking when I hit the brakes

My first though is, the brake controller needs to be set to a higher "gain". Have him max it out on #10 once and try the brakes. See if he feels the trailer jerk to stop then?

If he uses the manual switch and the trailer brakes work, then the trailer brakes are good. If it then doesn't work when using the foot brake, it's the truck/controller.
I think dealers hate to work on these things because they aren't accustomed to them.

I think your dealer has it backwards.

If the trailer brakes work on manual, the trailer wiring is working properly as the trailer wiring doesn't know if it's the pedal or the switch activating the brakes (same wires from the plug to the trailer brakes).

Far more likely is it's in the truck as there are separate wires from the pedal to the controller vs the manual switch to the controller.

Update: checking the gain is a good first check. The wiring might be just fine but if the gain is turned way down, you won't feel the brakes grab.

My controller has 2 additional ways of controlling how sensitive the brakes work.

Hi.. is the brake controller intergrated in the truck? If it is go into the system brake menu and determine what it is set on /light trailer, heavy trailer, should be a scale 1 to 10 for each. Set it up to where you can get he brakes to grab.. I go 10mph. You then back down the setting, to where you get a soft smooth stop. I really do not think the dealer.like to work with this stuff. Jim2007

Jim2007 is onto something. Check the adjustment for trailer size/weight.

Also: Ford's integrated brake controller is designed so that you DON'T feel the trailer braking and pulling you back, and you DON'T feel the trailer pushing the truck. If the system is working correctly, you shouldn't feel it at all.

Well what is the gain set on.

On my f250 there is a plus and minus button just underneath the manual slider pushing those buttons changes the gain and the gain setting is shown on the dash as it is changed.

The OP mentioned that his son "felt" the brakes working when manually activated. That's a mild way to describe what should be brakes locking up when moving 25ish MPH and then manually activating them. A number of suggestions.
1. Check if your controller is set to the correct weight of trailer.
2. Jack up the trailer and adjust the brakes. This should be done every 3,000 miles or so. Those brakes wear and don't automatically adjust.
3. Accelerate to 25MPH and then fully activate the brakes manually, they should lock up or very nearly so. If they lock up, back off the +/- adjustment a bit.

The Ford IBC is so smooth you will not feel the action of the trailer brakes. There is NO grab feeling. I thought the same thing with mine. It is totally proportional to the brake pedal pressure applied and integrated into the ABS system. Page the DiC to the brake controller and press the brake pedal and you will see the gain increase as you put the pressure on. I set mine at 9 and forget it.

Has he opened the Ford manual and read the complete section on how to set up the integrated brake controller?

Next I would want a clamp-on DC ammeter to see if 3 amps are getting to each trailer brake while parked and manually applying the brakes.