I must be missing something. Is everyone who has Motion 5 getting messages that say there are system updates ready and then acting on that take the time to download the material, only to find an hour later that the updates are still wanting to be downloaded?
And, I can't see anything in the Motion File menu which offers me any options re Supplemental Material. Perhaps the menu is smart enough to lose the option to do a download once it is completed.
What am I missing?
Look in the Motion "app" menu, not he File menu.
You may also want to try two other things if you still have trouble.
Download the free "Preferences" app from Digital Rebellion (dot com) to trash Motion's preferences.
If that doesn't help, move the Motion app from the Applications folder, to the Trash. Launch the App Store, go to the Purchases tab, Motion will now have a "Download" button to the right of it. Download it and let it install again fresh.