Can't retrieve some album artwork. Error: "The requested resource was not found"

The "Find Artwork" command doesn't work on some albums, even though they're available on the iTunes music store. Some of the albums are a few years old, but two of them are recent releases (after July 2015). I'm running the latest iTunes and OS X on my iMac.

When I ripped the CDs, no artwork appeared. When I try "Get Album Artwork" I get the error "The requested resource was not found".

As an experiment, I took my entire library and added it to another Mac - one that I had never used iTunes on. The same albums are unable to get the artwork.

Is anyone aware of a fix?