Album art does not show up in Music

My music library on mac suddenly stopped showing album art. The album covers are still associated with the files, adding the files again does nothing. I've added all my music manually, so I don't know if it would affect the regular music, and I don't use music on my phone so I don't know about that either, but when I try putting songs on my iPod (nano 5th gen) the album art is still the default cover.

It's like this for every album.