In a hex dominant parametric mesh, the boundary layer does not appear. It was created with the parameter of relative size deactivated.
The issue was in the mesh quality controls, as my mesh were not too good, and as a result, it erase the boundary layer as it does not fulfill with the requirements.
On the other hand, I had different refinement levels, and with the usage of an absolute boundary layer, leads to a heterogeneous boundary layer.
Thanks to Igor I could fix it.
Hi @simprocess, thanks for posting on the forum and welcome to the SimScale Community 
That’s great to hear and happy your problem was solved! Now other users can also benefit from the solution.
Cheers
Igor