That would be an issue with the files, or the coding itself (which would be the error of the distributor). Most likely though, the .png or .mat files which should have come with the file pack (which are the textures) you did not move into the items folder like the other mesh files. Another possible solution is just restarting the game if all the correct files are in the folder it should be able to figure out how to apply the textures to the meshes itself.
So do these things if you haven't yet:
Restart the game
Look in the items folder and make sure every .mesh file has a matching .png and .mat file. (If not, just unzip all the files again in the correct place)
Confirm that you added all the necessary code to the items.cfg file
If all else fails, then I would message the distributor and tell them that the textures aren't working for you, and they will probably have a more direct solution to the problem.