I have been having troubles getting new contributors to show up in the Edit Flow Notifications. The issue is as follows:
When I create a new Contributor User on my WordPress site and then try to assign that person as the "author" of an article and check their name off in the Notifications, they do not show up.
The only work around I have is to set that User as an "Administrator" so that they will show up in the "Author" list and "Notifications". I then need to change their User account back to "Contributor" so they don't have full Administrator access to the site.
It seems to work as a "work around", but not a great solution.