Hi,
It looks to me like the allow resellers to backup/restore users feature has been disabled from within the administrator settings in the admin level of DA.
You'd need to contact your admin to see if this is the case.
If so they can restore it or allow you to.
I'm not 100% sure if this scenario produces this error message as it's a global setting not reseller specific and I don't have a DA test box or if the user can restore themselves from their create/restore backups .
Rob