Backup operation failed with the messages: The staging location must be an existing UNC path. Please review the value of the key 'spFileRestoreTEmpFileDirectory' in the backup service cconfiguration file.
In this case the user needs to identify the primary server.
On the console go to > Configuration > Fault Tolerance
After the primary server have been identify, User need to go to the backup service installation folder
With a text editor as Admin open the File 'PBbackupservice.exe.config'
The user need to enter a UNC path with read and write permissions for backup service account, that path will be used as a temporary location to backup service application data, when the operation is completed it will be cleaned up.