Get Album Artwork doesn't work

I use 'Get Album Artwork' from the contextual menu to get artwork from the iTunes Store; but it never finds it no matter what album or track I select although I can see in the Store that the album is available (with cover art). I have a valid iTunes account although I never buy music from it - these are my own ripped CDs. I haven't used this facility successfully for a long time; but it used to work fine.

I'm in Denmark, so I'm using the Danish store.

I don't want embedded artwork and I don't mind if some covers are not available; but I would like the ones that clearly are!