Featured Images in Pages and Posts won't show!!

Hi, I'm having a huge problem setting featured images (NOT featured header images) on my pages. Once I set the featured image I want in the page builder under 'featured image,' no image appears in the page once previewed or published. I can't think of what I'm doing wrong- Is there a button I have to select to enable featured images? Do I have to select something in the 'Fabulous Fluid Options' at the bottom of the page builder? Maybe something in the customizer? Is there a minimum image size? I've a fairly experienced Wordpress user and it's never been this difficult! Please help--I've been troubleshooting for days now! I'm trying to get a featured image like this demos have: https://catchthemes.com/demo/fabulous-fluid/uncategorized/template-sticky/ Thank you!!