When you attempt to add new users but the system gives you an error telling you that this user already exists, it is likely they exist on other projects in the same company domain.
What can I do?
Once you click Add Users, a table of existing users from the same company appear. Select the users from the list, scroll to the bottom, and click Add Selected Users to Project.
Note at (2) you may disable Email users login details if you do not wish to trigger an account detail notification.
That's a terribly long list! Can I search users from the list?
Sure thing, use the fields Name and/or Email to filter on the user you are looking for. Another option is to use the search function of the webbrowser itself; Ctrl + F (in Windows) or Command + F (in Mac).
Are you a Company Level Admin? Click here to see how to manage users at company level.