I originally added two categories without sub-categories. When I added more categories, only the first two were displayed when 'Show Categories' was selected. Even deleting one of these displayed categories did not change anything. In options I unselected 'Show Categories', saved, went back to select 'show categories' in main options, yet now there is no button displayed in top navigation. I have plenty of categories created, set 'Category View' to -1, and when uploading a document I can select one of my five created categories.
This is not an issue for me being able to go live with your product, but I am still confused why 'Show Categories' is not displaying along Top Navigation, and when Startup Screen is set to show categories, only two original display.