Backup Global Settings only in Virtualmin, Backup Failed: No features selected to backup

I want to backup my global settings but think I do something wrong can some one help me please.
Following this tutorial, section Backing Up Global Settings

I am getting the error: Backup Failed: No features selected to backup, I have done exactly step 1 to 3, not sure why it doesn’t work.

Virtualmin, Backup and Restore, Scheduled Backups.
Create a Scheduled backup.
Virtual servers; Only selected [none], un-ticked Include sub-servers of…, Any plan.
Features and settings: Only those selected below, None for the section of Features to backup, All selected in the Virtualmin settings to also backup!
Destination to my backup server single archive file

after saving, the Backup Now button is grayed out, but trying to run in background fails with the error.
It still fails if I select Backup all Features, seems it needs a virtual server domain to work, but I want only the global settings, what am I doing wrong?