Images not showing up for slider or grid in featured content

I’ve installed twenty fourteen but images don’t appear in the featured content slider or grid (I’ve tried both). My prior theme automatically took the first image as the featured image if no featured image is specified, so I didn’t specify featured images. I figured that twenty fourteen must need the featured image specified, so I specified them in the admin panel. But they still don’t show up on the home page slider.

Also: I’ve assigned the “featured” tag to post intended for featured content.

What am I doing wrong?