Publisher account is getting a permissions sync error (see attached) which does not allow syncing of a layer they own (published).
User accounts, who the layer is shared with, do not have the sync issue.
And the problem is only on Android Collector not Apple Aurora Collector. So a very specific issue that a Collector tech should be able to remedy quickly.
It seems to be related to permissions issue on ArcGIS On-line on Chrome. The publisher account cannot see feature layers created by the publisher, whereas user accounts can. Again - this is another big clue to what is going on.