Not able to add material to the layer

Everything was working fine couple weeks ago, to add materials to layers. But now it just stop working. I have tried reset to factory default and delete the program and reinstalled again. Nothing works. Please let me know what’s wrong. Thanks!

Assuming you are running V7 and using the Rhino Renderer…
In Rhino Options > Plug-ins, are these plug-in enabled and Loaded?