An error appears when I try to delete an Organizational Unit with no users.

You will not be able to delete the organizational unit if it is added as “Additional post” for users.

Please access the “CloudGate UNO Address Book” and click on the organizational unit to see if there are any users in the unit.

If any users exist, please check the “Additional post” in CloudGate UNO Administrator Site > Users > click the userID > Additional post.