Remove featured photo from blog post

Try this CSS code in the customizer:

body.single-post div.post-thumbnail {display: none;}

Sorry, my code is not a solution.
Simply don’t insert the same image again, if you used it as a featured image!

No, that code doesn’t work.

Don’t have this issue with other themes. Can I ask for a refund on the pro version? Is that possible? I’ll delete the theme from my blog if that is possible.

I would like to know what causes the issue. If you have a featured image, don’t insert it again into the post! What happens in that case?

Second solution: if you have inserted the image into the post, don’t use it as a featured image as well, because then it will be displayed twice.