How do I get the Featured Image Post URL link to work?

Hello! I want readers of my blog to be able to click to my full posts by clicking on the Featured Image of each post in the blog feed. In other words, I want to make the featured image into a hyperlink that links to the post itself.

I assume this function is controlled by the Link URL field in the Featured Image area. I set mine to Post URL and saved all changes. Yet it doesn’t work. What’s going on?

And while we’re on the subject, once I get that issue solved… I would like ideally to have a hyperlink-hover effect on the featured image, like as a little border that appears around it when you mouse over it to indicate it’s a hyperlink.