Hello @Syed Ammar Haider ,
Thank you for posting here.
For your issue, you can try the following steps to see if it helps.
1-If the secondary domain controller is a virtual machine, disable the Network card.
If the secondary domain controller is a physical machine, unplug the network cable.
2-Logon the secondary domain controller using cached domain Administrator.
3-Enable the network card if it is virtual machine or plug the network cable if it is physical machine.
4-Opem CMD (run as Administrator).
5-Run the command below on the secondary DC.
Netdom resetpwd /s:target_server /ud:mydomain\domain_admin /pd:*
In your case, target_server is the first DC (PDC) name.
/s:server is the name of the domain controller to use for setting the machine account password. This is the server where the KDC is running.
/ud:domain\User is the user account that makes the connection with the domain you specified in the /s parameter. This must be in domain\User format. If this parameter is omitted, the current user account is used.
/pd: specifies the password of the user account that is specified in the /ud parameter. Use an asterisk () to be prompted for the password.
For more information above reset machine account passwords of a Windows Server domain controller, please refer to link below.
Use Netdom.exe to reset machine account passwords of a Windows Server domain controller
If it works above (I mean you can run the command successfully), then sign out and sign in again using domain administrator to see if there is no error message.
Hope the information above is helpful.
Should you have any question or concern, please feel free to let us know.
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