What it Means
The "RPC Server is unavailable" error means that Right Click Tools is having trouble connecting to Remote WMI to run the action that was selected.
First, verify if the Remote Procedure Call (RPC) service is 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. Please verify that Remote WMI is configured correctly in your environment and not blocked anywhere else on your network.
For investigating potential firewall issues, Dell has a knowledge article that goes more in-depth here: Troubleshooting "RPC Server Unavailable".