I bought an alum keyboard from eBay (link). I got the keyboard in the mail today and I plug it in, but it's not working. It doesn't read any keystrokes at all on my iMac or on my Mac Mini. What do you guys think could be wrong with it? It's in a really nice condition and looks like it's hardly been used. The wire isn't frayed or anything. I have already contacted the seller and am waiting to hear back from him.