Veeam Error: The RPC server is unavailable. RPC function call failed

Situation: The client receives this Error: The RPC server is unavailable. RPC function call failed. Function name: [InvokerTestConnection] from their Veeam Backup. Target machine: Host05.

Troubleshooting 1: Veeam Backup & Replication may not be able to reach the Veeam Installer Service on the remote machine.

To fix this issue, please follow steps:

1. Make sure the Veeam Installer Service is running on the machine specified in the error, Host05 in our case.
2. If the Veeam Installer Service cannot be started, check if another application is using the default port (6160) used by the Veeam Installer Service.Use the following command to list the PID of the application using port 6160:

   Get-Process -Id (Get-NetTCPConnection -LocalPort 6160).OwningProcess
   

   Alternatively, check within the Listening Ports section of the Network tab in Resource Monitor:

3. 3. If the Veeam Installer Service is running on the remote machine, run the following PowerShell command on the Veeam Backup & Replication server to isolate the connection issue:
      Replace <remote_machine> with the hostname, FQDN, or IP shown in the error.

   Test-NetConnection -ComputerName "<remote_machine>" -Port 6160

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   4. If neither PowerShell nor Veeam Backup & Replication  can reach the port and the Veeam Installer Service is running on the remote machine, investigate whether a firewall is blocking connectivity between the two machines.

   Other possible resolutions:

   • The Netlogon service is not running and is disabled.
   • Antivirus on the remote machine is preventing the VeeamDeploymentSvc.exe from being run.
     Process location: C:\Windows\Veeam\Backup
   • The Veeam Installer Service is not installed. In such a situation, edit the machine’s entry within the Backup Infrastructure > Managed Servers section and next the pages of the Edit Windows Server wizard to force the package to be redeployed.
   • The Veeam Installer Service package was partially updated. In such a situation, uninstall the Veeam Installer Service from the remote machine. Then edit the machine’s entry within the Backup Infrastructure > Managed Servers section and next through the pages of the Edit Windows Server wizard to force the package to be redeployed.