After using dcdiag tool (e.g. “dcdiag.exe /V /C /D /E /s:dcname”, the following error message may appear: “Could not be queried, error 0x6ba "The RPC server is unavailable.”
Usually, this issue occurred due to Microsoft Windows Firewall forbidding unhallowed TCP/IP traffic. To resolve this issue, use one of the following technics:
1. Disable the Microsoft Windows Firewall (Less recommended).
2. Add "Remote Administration", as a firewall exception.
3. Add the following TCP/IP Ports: Configuring System Service Firewall Rules , as a firewall exception.
Note: Third party applications (e.g. Antivirus etc.) may also block the TCP/IP traffic.