How to Restoe File Tree Panel

Using V11 Win 8.1
Somehow I closed the file tree display panel and I've been unable restore the file tree panel. I've compared the preferences options side-by-side on a PC where the file tree panel is displayed and can not find any differences. I haven't made any changes to the lister configurations. How is the File Tree pane turned on and off?

With the default toolbars:

1 Like