WD My Book format help for Mac Yosemite

I, too can’t get my My Book for Mac working and in a Yosemite environment.  Been on WD tech support with tech 2Xs for an hour each.  At the end of it could drag and drop a doc to the desktop WD app.   Techs were certain it would then perform a full backup just perfectly and left the conversation.  Backup failed with message “Unable to complete backup. An error occurred while creating the backup folder”.  I am at a total loss.