Album Artwork Missing

[Adrian992]

I have been using Synology Media Server with my Synology NAS DS220+ and a Cambridge Audio CXN V2. I found that I could not see any content in the Media Library section of the Stream Magic App. Cambridge Audio suggested I install MinimServer on my NAS which I did and now I can see my Media Library and can select from Albums, Items, Artist, Date, Genre, All Artists, Composer, Folder View.
However, not all of the Album Artwork is visible.

My music library of 271 Albums was copied from the Music Media folder on my Mac and if I look in that folder on my Mac the album artwork is visible for all the albums. Note these are albums that are CDs that I ripped onto my Mac and whilst I can also use AirPlay to play to the CXN, I wanted a stand alone playing capability from the front panel of the CXN for my wife to use without the need for my Mac or iPhone to be needed.

I have MinimWatch installed and activated the Trial Licence but the only change I have made to the default configuration is to set indexArtwork=Auto in Properties>Advanced

Is there something else I need to do so that the artwork for all my albums is displayed?