Either this domain controller has no replication partners, or the site this domain controller is in has no connection objects to other sites. Changes will not replicate from this domain controller to all other domain controllers in the forest.
This problem requires immediate attention.
Failure to resolve this problem in a timely manner can lead to lingering object problems and password synchronization problems, among others.
This is usually caused by an invalid manual configuration of the replication topology. There are some domain controllers that do not have connection objects that will allow them to replicate with all the other domain controllers.
Check the replication topology to ensure that there are connection objects - particularly between sites - that will allow replication to occur.