Hi Guys, I'm new to the forum, and I was so frustrated by this problem which only started affecting me after I upgraded to iOs 14.5. I add my own photos to the songs in my music collection, and after a recent refresh of some on iTunes on my Mac (Song >Get Info >Artwork / Add Artwork), I synced my iPhone only to find that they did not transfer. The music on my iPhone had all the old artwork. I read many articles on this, none of which solved the problem for me; but then, on a hunch, just tried deleting all my songs from my iPhone, restarting it, restarting my computer, then syncing. It worked. Good luck!