One problem with iTunes is it does not like updating metadata of files once they are in iTunes. It assumes the only changes you will ever do is by using iTunes. So you may need to remove the album from iTunes, move it out of sight of iTunes, delete it from iTunes. And then reintroduce it.
Also how are you adding your artwork? Embedded? cover.jpg? folder.jpg? Those old apps like iTunes\WMP are fussy things. They also get extra confused if you have PNG files, too large images or things like that.
Two of many threads with the same issue: Picard to iTunes (apple music) embedding art images not functioning and "Syncing" iTunes Cover Art with Picard