Back button in Finder occasionally disabled; always go up one step in hierarchy?
The back button behave the same way in Windows &amp; Mac, it returns to where you last looked. If that was the only place you've been, it has no history.

You can test that in Windows by either selecting different locations from the sidebar shortcuts, or by opening a new window by right clicking a folder &amp; selecting Open in new Window. It then will not have a History.

To navigate the hierarchy on Mac there are several options...


 Cmd ⌘   ↑  will climb the hierarchy,  Cmd ⌘   ↓  will descend it.  
From the Finder window toolbar, there is a hierarchy drop-menu -   
Even without the toolbar visible,  Cmd ⌘  Click on the folder icon at the top of any window will drop the same menu.
From the Path bar underneath, you can double click any item to open that point