Featured images not showing

Hey.

https://networkbees.com/

Have been using the Suri theme for a while. The only problem that I have is that a large number of my featured images do not show up, despite the fact that I have “Display Thumpnails in single posts,” selected.

Its kind of frustrating. Here is one great theme, and it has to have this problem. Some of the images actually show. But the rest do not. Is there something that I am doing wrong? I have tried playing around with the sizes of the images but that hasnt worked.

I have also tried setting the post type to “image.” Still no success….