Symptoms

The error pops-up when trying to create a file system backup set (at the time when attempting to expand Microsoft Windows Network to select the backup source server).

Cause

The DS-Client runs on Windows 2019.

Workaround

Open Server Manager, navigate to Add Features pane, expand "SMB 1.0/CIFS File Sharing Support" and tick 'SMB 1.0/CIFS Client', and continue with the remaining screens to complete this feature installation.