Ran a DCDiag on my Active Directory Domain Controller.
DCDiag is a quick way to check the health of Active Directory.
While reading through the report I noticed that the replication to my Forest controller was not replicating to my Domain Controllers.
See the date and time when the last replication was received:
It turns out that the NetLogOn service on the Forest controller was in a Paused state.
NetLogon service maintains a secure channel between the Forest domain controller and the domain controller for authenticating users and services. If its stopped or paused, unable to register DNS records or authenticate users.
Once this has been resumed, replication between the Forest and the Domain Root will work.
You can verify this by open a Command Prompt on the Domain Controller and running the following command:
repadmin /syncall
1 Giant Nerd 