Q: The music on my iPod Nano suddenly disappeared and now iTunes doesn't seem to recognize my iPod when I try to connect it.

The iPod's storage may have data corruption.  Try putting the iPod into Disk Mode.

Putting iPod into Disk Mode - Apple Support

If it goes into Disk Mode, connect to computer running iTunes.  If iTunes picks it up, it may prompt you to do a Restore with a message about "recovery."  A Restore will erase the iPod, reinstall its software, and set it to default settings.  You can then reload your music.