It turns out that of the three albums I downloaded at work, I already have two. LOL. At least Amazon has the courtesy to provide a notice that a CD or DVD has already been purchased. I need to send a suggestion to HDTracks about that.
For the third album, 14 of the 15 tracks initially displayed. I then powered off the Lumin, removed the drive, powered on, reattached the drive, and all 15 tracks displayed.
The initial procedure was leave Lumin powered on, remove the drive, copy the new album to it, reattach drive to the Lumin, check the track listing, wait 15 minutes to see if it updates. Then I did the above sequence.