Adprep was unable to extend the schema. Status/Consequence The schema master did not complete a replication cycle after the ...

Adprep was unable to extend the schema. [Status/Consequence] The schema master did not complete a replication cycle after the last reboot. The schema master must complete at least one replication cycle before the schema can be extended. [User Action] Verify that the schema master is connected to the network and can communicate with other Active Directory Domain Controllers.  Use the Sites and Services snap-in to replicate between the schema operations master and at least one replication partner. After replication has succeeded, run adprep again.