Can't manage to have the head to rotate based on the view

Hello,
I am making a FPS in coop, and would like the player to see where other player are looking at in a nice manner.

I am trying to setup the head to always look at a target, and planning to add some player rotation later on after a certain threshold.

I setup some initial package and basic animation, then added a new Rig Setup, created some AIM Constrain for the head and torso, and made it look at a game object. It worked, so I placed that gameobject as child of some object inside my model (not on rig but on the model itself)

I rotate that gameobject via script, and therefor the AIM target move with that rotation.

The problem is, my head do not move. It only move if I move it in the scene in polaymode, but never move when it is rotate by code.

I am very unsure as to why, is there some mandatory hierarchy to respect ?

I attached some video below with the details .