iPod 120GB Classic is recognized by iTunes, but it won't sync. I ran diagnostics. The device connectivity test showed the iPod, but when I ran the device sync test, it said no device was found. It didn't sync prior to Windows 10 upgrade.

The iPod needs to be set up to sync automatically. If it is not, clicking Sync does not sync anything.

Select the iPod in iTunes, so that you see the iPod's settings screen in the iTunes window. Along left side of window, in the sidebar, under Settings, click Music. To the right, you see the iPod's Music settings screen, where you tell iTunes how to sync songs to the iPod.

NOTE: Any songs on iPod that are NOT in your iTunes library (on the computer) will be lost. If all songs are in your iTunes library, no problem.

At top of window, checkmark the box for Sync Music. This turns ON automatic syncing. Below that, select the option to sync Entire music library, if you want "everything" in your music library to sync. At the bottom, click the Apply button.

Going forward, when you make changes to your iTunes music library (like add new songs or update a playlist), iTunes automatically updates the iPod with the same changes when you connect it (or click Sync if already connected).

Hi! Thanks a lot for your answer I had the exact same problem. But here's where it gets more difficult for me: I have a new computer and I'd like to transfer the library from my iPod to the new library. Is it possible? Or do I have to transfer all this music in another way? (ie using an external hard disk). Thanks for your answer !

That's actually the "opposite" problem. 😉

iTunes syncing typically works in one direction only, from computer to iPod. That is by design. The exception is songs purchased from the iTunes Store (because iTunes can verify ownership for those songs). However, there are third-party methods and utilities that can transfer from iPod to computer. If you do an Internet search on something like "ipod transfer," you should get some useful links, including a CNET article on the topic.

After your iTunes library has all of your songs, you can do what I described in my previous post to set your iPod to sync your complete iTunes music library.

Haha, actually I had the same problem as the one above on my former computer (not being able to synchronise), and now I have this. The CNET link helped me, thanks a lot !

thanks that fixed it. should have known.