SSO integration with Agari only handles authentication, not user management. After enabling SSO all current users will receive an email to reactivate their account. To add a new user, first, add them to the correct AD group and then create a user in the product. An email will be sent for the user to finish setting up their account. This will bind the product account to Active Directory.
The invitation is good for 30 days. If the user does not accept the invitation and finish setting up their account you need to resend the invite by going to Manage > User > Select User and Resend Invitation.