In the shader that comes with assets when importing into houdini - the image_normal node is fed directly to the mat_surface node (the shader itself), this doesn't work and the surface becomes completely matte/rough.

It needs a mtlxnormalmap-node in between the image-node and the shader to do the normal map correctly. And the mtlxnormalmap itself needs a mtlxnormal-node fed into the normal-slot. Attaching screen shot how it SHOULD look like.