Check that iTunes has been configured to use this feature. You can enable this feature in iTunes Preferences:
- Open iTunes Preferences
Mac: Choose iTunes > Preferences.
Windows: Choose Edit > Preferences.
- Click Store.
- Select the "Automatically download missing album artwork" checkbox.
iTunes will only download album artwork for songs that it can find in the iTunes Store. iTunes will check each song in your iTunes library and attempt to match it up with a song in the iTunes Store. If the data matches, iTunes will download the album artwork from the iTunes Store and add it to the song in your iTunes library. If iTunes does not find a particular song's artwork in the iTunes Store, you will not see an alert message. iTunes simply does not download artwork for that song.
Note: You must have an iTunes Store account and have logged into the account on the computer you are using.