Missing Artwork

Some Artwork dont show up. Im Using Rekorbox 6.6.1. So I've started all over with a pristine re worked collection. Fixed all Id tags including Artwork, renamed files and placed them all in an external drive. Deleted everything in the RB Collection, and imported all the "cleaned" files.
After import and analysis I can see all of the files (couple thousands) and only some of them show the Artwork the *.flac files do contain. What's wrong? What should i do to fix it and show all the artworks.