My Cloud app & displaying itunes cover art

I’ve just moved my entire music collection from my PC to the WD My Cloud. When I access the music on the app on my iphone, from all the folders of artists I have (several hundred) only one of them displays the artwork. So this one artist folder has about 10 abums in it and for each track the app displays a small pic of the cover art but it doesn’t do this for any other artist. However itunes and my sonos do display all the artwork - what am I missing?

The album art needs to be embedded on the MP3 file for it to be recognized on the My Cloud app. Try doing a Google search for more information on this.