If you see that one of your releases is in distribution error due to a missing Apple/Spotify ID, here is how to fix it most easily:
Go to Catalog Management > Artists > the artist missing an Apple/Spotify profile ID.
Enter their ID(s).
Save your work.
Go to the release's Distribution page (NOT the main Distribution section; it's rather the Distribution tab/section of a specific release when you're viewing that release).
Select all DSPs that you wish to update.
Note: if you cannot find the artist in Catalog Management > Artists please open a support ticket and indicate:
The release ID or UPC
The name of the artist