Since updating to iOS 12 on my iPhone 6 I’ve had a major headache. Album art hasn’t been working for my iTunes match (iCloud) music library, and I’ve only been seeing the standard iTunes missing artwork icon for my songs & albums.
I even re-subscribed to Apple Music to see if the problem was iTunes match only, but it also affected most of the music I streamed from Apple Music too.
I’ve managed to find a really simple fix for the album artwork problem.
Head over into settings and click on the music tab. Once there, you need to disable iCloud music & Apple Music by clicking the toggles. Immediately after disabling iTunes Match (iCloud Music) and Apple music, you need to restart your iOS device. Do this as soon as you disable the toggles, that way you will stop iOS pruning off corrupted artwork files.