I reset my iPod but music can not be added back on

Make sure you're using iTunes or Apple Music to sync your music with the restored iPod. Connect the iPod to your computer, open iTunes, select the device, and choose the music you want to sync. If you encounter issues, ensure your iTunes is up to date and your music files are in a compatible format.

Reset and Restored are two different things:

• • A Reset is performed on the device (basically, powering it down fully and then turning it back on) and simply puts all the settings back to a known state so that the iPod knows what it's doing. It does not affect the content of the iPod.
  • A Restore is carried out by using iTunes and deletes all the content from the iPod.

If you used iTunes to restore your iPod, you will need to set up the Sync options as though the device is new.