I have a problem with adding another child domain controller for my lab. In my scenario, my other child domain controller is also online and one of the parent domain controller is also online.
What other finding I have to make sure is that the DNS is pointed to the child domain controller.
Also, I have checked the debug log in C:\Windows\Debug\Dcpromoui.log. It seems that the error is appeared similar on the error above.
In the error above, when we further look, it successfully queries the SRV record of testbranch.netoverme.local.
My solution is by checking the Domain Naming Master role has be to online and contacted. Domain Naming FSMO role is responsible to add and also remove domain. In my case, I have 2 parent domain controller (dc1.netoverme.local and dc2.netoverme.local) and my child domain controller is testbranch.netoverme.local. my scenario above is to add another domain controller to child domain controller of testbranch.netoverme.local.
After I can ping dc1.netoverme.local which hold the FSMO role of Domain Naming Role and make sure the port and firewall is not blocking, now the domain controller can successfully add. One more thing FSMO role has to be contacted or online, DNS delegation has to be done for adding all DNS record in the parent domain.