iPod Classic won't sync with iTunes (2019)

I realise several people have had this problem but I'm hoping there really is a fix available now. There is nothing wrong with the iPod so please don't suggest all the usual checks/reboot/reformat etc...

iTunes recognises the iPod and it seems to sync with it. I can select the iPod from iTunes and see the music on it (and play it), BUT when I disconnect it, the iPod is showing "No Music".

If I use Disk Utilities on the iMac with the iPod connected I can see that there is nothing showing on the iPod under "music" but it is showing data stored under "other" (There is nothing else stored on the iPod)

I am thinking that maybe the latest version of iTunes stores music on the iPod in such a way that the software running on the iPod can't recognise it or iTunes puts it somewhere it can't find it?

The other thing is that if I try to "Restore iPod" from iTunes, it fails ("could not be restored") and reports an unknown error 1430 - plus when you select "more info" just leads to "The page you are looking for cannot be found" on Apple website!

Any of that make any sense, and anyone have any ideas please?