Compilations split up separately in Itunes

Please help, this is so frustrating. So I've read all sorts of other threads, and tried everything they suggest but I can not group my compilations into the same album. And nearly all of my Itunes library are compilations.

I've tried clicking all of the songs from the same album, 'Get Info' and clicking the 'Album is a compilation' button, I've changed the album artist to the same, and every time I click OK, it goes back to how it was, and won't group them together.

My Itunes is a mess, and I've had to resort to putting them all in playlists, but I'd really like to fix this.