There should be a place under the front of the seat where each individual seat motor connector comes together to connect to the wiring harness that comes up from the floor.

The headrest motor is mounted in the seat back, to the frame of the seat. It has a set of wires that goes down to the junction point described above.

You need to determine which wires they are, and if there is power to the junction point from the switch. Using jumper wires to deliver power and ground to the motor wires directly, so the switch is bypassed, will allow you to determine if the headrest motor and its drive system works.

What you have done so far is good, but now you need to isolate it further at that junction point, which will be easier if you unbolt the seat so you can tilt it back a bit for better access to those connectors under there.

If it has memory seats, it has more wires under there, but the basic approach is the same. The extra wires are because each seat motor has a position sensor on it.

It will help if you can locate the wiring diagram to help identify wires by color.