The 'RPC Server is unavailable' error indicates that Right Click Tools is having trouble connecting to Remote WMI to run the selected action.
TIP: This error is best resolved by deploying Recast Agents.
Troubleshooting Steps
First, check that the the Remote Procedure Call (RPC) service shows as 'Running' within Windows Services.
If the service is running and you're still encountering the error, there's most likely an issue with your firewall configuration. Verify that Remote WMI is configured correctly in your environment and not blocked anywhere else on your network.
For further information on investigating potential firewall issues, see Microsoft's article: Remote Procedure Call (RPC) errors troubleshooting guidance