WMI: The RPC server is unavailable. (Exception from HRESULT: 0x800706BA) throws when try to connect to remote machine

If you under Win7 you must run app as an administrator. You can also try different values for connOptions.Impersonation property. Did you open RPC port on a remote machine? Try turning off firewall altogeter on both machines.

Also, You need to enable Windows Management Instrumentation (WMI) rule in windows firewall.

1] Windows Firewall.
2] Allow app or feature through windows firewall.
3] Enable Privilege for Windows Management Instrumentation(WMI).

To enable or disable WMI rule using Windows firewall

1. In the Control Panel, click Security and then click Windows Firewall.
2. Click Change Settings and then click the Exceptions tab.
3. In the Exceptions window, select the check box for Windows Management Instrumentation (WMI) to enable WMI traffic through the firewall.

To disable WMI traffic, clear the check box.

You can also enable or disable WMI traffic through the firewall at the command prompt.

To enable or disable WMI traffic at command prompt using WMI rule group

Use the following commands at a command prompt. Type the following to enable WMI traffic through the firewall.

netsh advfirewall firewall set rule group="windows management instrumentation (wmi)" new enable=yes

Type the following command to disable WMI traffic through the firewall.

netsh advfirewall firewall set rule group="windows management instrumentation (wmi)" new enable=no