Message:

Can not update different Settings. There is already a session with a user.

1. It is because there is already one session (with this user with different ou  or  period)  which is not closed.  (Kindly advise all the user to log off their session properly) . You (Admin User)  need to login  and go to logged in user screen. Select the user in user list and click force log out
2. Then ask the user to save  screen
3. This may happen if the user have the open session in another system also.

No enough leave