MusicBee shows no artwork when whole album is selected because Composer tags are
mixed. Artwork is shown for albums that have only Track title and Track tags different. All other tags are identical for all tracks on this album, including artwork. I don't know if issue is there when some other tags are
mixed (e.g. Conductor). MB version 3.1.6287
Edit: I just realized that this is not Id3v2 but MPEG4 tagged album, but I checked with another MPEG4 tagged album and artwork is shown normally for whole album, but that album has no mixed tags except for Track and Track number