Which post are you referring to so I can take a look?
The featured image doesn’t display at all times, it depends upon the post format. Each post format displays differently with the image post format displaying the featured image on archive and single post pages.
The featured image doesn’t always show for posts. If you’d like to display the featured image on the homepage and single post page, the post format would need to be changed to an “Image”.
I’ll add a ticket to our team tracking system and see if we can come up with a way to allow the featured image display to be set somehow. We need to keep backward compatibility in mind so featured images aren’t appearing suddenly for those who don’t want them.