Hi there Kangeroo69,
You may find the troubleshooting steps in the article below helpful.
I have done all these things some in conjunction with Apple however none worked finally managed to restore Ipod Classic though a tablet but now it am getting message 1621 - and still not recognised by I Tunes on my computer - reinstalled I Tunes updated all the drivers etc. Got it to synch with I Tunes on Tablet but then it would not copy the music and then everything disappeared from the Library on their - nightmare -
I Tunes can recognise my Ipod Touch and Iphone - so it cannot be the connection etc. must be something in I Tunes to do with the Touch ?