This can happen when the system shows the user as invited, but they haven't received/accepted the link. It should show a list of 'Invited Users' under users. If the user has accepted they would show under registered. In order to verify what is happening in this particular case I would need the property name and users email. We may need to manually send the email invite link to the user. I recommend reaching out to Customer Care. They would be able to identify the issue and provide a manual invite link if needed.