Have invited collaborators to view a few libraries. On my end, it says they were invited or "previously invited" when I re-enter their addresses.
When they receive the email and click "Start Collaborating" the Libraries still don't show up when they are active in an app or in the Creative Cloud site/app. They don't receive a notification in the CC site/app either. So in the end they still don't get access when the expected result is for them to receive access when inviting via share> entering their email address.