The GlossBsdf node is not working because you have a Scatter node mixed with your Specular Color map.  The Scatter node is predominantly a diffuse-oriented node and shouldn't be plugged into any specular connector; they are incompatible.  What you see working is the Alternate_Diffuse channel.

My recommendation: remove both the Scatter and Blend nodes and rerender.  You should see a difference.  However, realistically, hair is never that shiny under normal lighting conditions. You would like some specular highlights, but I have a suspicion the node will be too overpowering.