Gallery thumbnails not showing up

Whether I use ‘Portfolio’ or ‘Portfolio Gallery Type’ (on my ‘Projects’ page) in the page attributes, none of the thumbnails show up. ‘Portfolio’ gets me the description under where the thumbnail is supposed to be, but no image above it.
I’ve created 4 portfolio items under ‘Portfolio’ in the dashboard.
I’ve uploaded an image under ‘Different Featured Image’.
The ‘Disable Featured Area with Video or Image’ is not checked.
What am I missing?