The message: “Active Instance not set. To set an active instance use "Activate Instance ".” is displayed when you attempt to perform an authoritative restore with ntdsutil on a Windows 2008 R1 or R2 domain controller
Problem The domain controllers in your environment are either Windows Server 2008 R1 or R2 and you’re trying to mark an object or subtree as authoritative so that they will be replicated to the other