WMI The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)

I found the solution for this. I did it by enabling Windows Management Instrumentation (WMI) rule in Windows Firewall.

1. Open Windows Firewall.
2. Allow app or feature through Windows Firewall.
3. Enable Domain Privilege for Windows Management Instrumentation(WMI).

There are some other things also that you can check.

1. The remote computer is blocked by the firewall.
   Solution: Open the Group Policy Object Editor snap-in (gpedit.msc) to edit the Group Policy object (GPO) that is used to manage Windows Firewall settings in your organization. Open Computer Configuration, open Administrative Templates, open Network, open Network Connections, open Windows Firewall, and then open either Domain Profile or Standard Profile, depending on which profile you want to configure. Enable the following exception: Allow Remote Administration Exception and Allow File and Printer Sharing Exception.
2. Host name or IP address is wrong or the remote computer is shutdown.
   Solution: Verify correct host name or IP address.
3. The "TCP/IP NetBIOS Helper" service isn't running.
   Solution: Verity that "TCP/IP NetBIOS Helper" is running and set to auto start after restart.
4. The "Remote Procedure Call (RPC)" service is not running on the remote computer.
   Solution: Open services.msc using Windows Run. In Windows Services, Verify that Remote Procedure Call (RPC) is running and set to auto start after restart.
5. The "Windows Management Instrumentation" service is not running on the remote computer.
   Solution: Open services.msc using Windows Run. Verity that Windows Management Instrumentation service is running and set to auto start after restart.

The error The RPC server is unavailable. (0x800706ba) can occur when Windows Firewall (or any other firewall) blocks WMI connection. See Connecting Through Windows Firewall and related articles.

The code is running fine when I'm adding domain admin under remote machine's WMI Control remote security property. please check below screenshot.

I doubt that this is really true. When you don't have permission to access WMI you usually get Access is denied error.