why doesn't my ipod classic connect to my mac?

Every time I connect my ipod classic to my macbook, it does not appear on my computer desktop or in iTunes. However, on the screen of the ipod it first says that it is connected and to not disconnect until ejected, then it says synchronizing, do not disconnect until ejected. I don't see how the ipod thinks it's connected, while the computer doesn't think so

What can I do to make the ipod connect? I have tried to see if it would work with another mac, but it would not.