Probably not enough geometry; remember, your Viewport Subdiv is set to 8 px.
Also check that all Textures, apart from Albedo, are set to Non-Color and make sure that everything is connected correctly (if the Normal output of the Scatter Node is indeed a Normal Map, then you shouldn’t connect it to a Bump Node.
And next time you add your .blend file (which is almost always a good idea!), please pack your External Files (in this case the Images).
