Album Artwork not showing only on mac

Hi

I got a major Problem with Rekordbox espacially on my MacBook, the Album Artwork is not showing or Loading dosent matter what I do. I read previous threads about this but nothing helped. The strange thing about it is that on my Windows PC everything is just fine. Most of my songs are bought from the iTunes Store so the files are definetly not corrupted or else. And the problem only appears on songs i bought from iTunes. Help Please