Need to click on featured image to see actual post

Hello,

When I create a post using the gallery option, it only shows the featured image. (When none selected it shows the default image). When I look for the post in my menu (made with categories), I need to click on the featured image to see the actual image gallery. What I want is all the images to be show directly with the gallery function.
I’m running the latest WordPress version. I’ve tried using different themes to see if there as any difference.

Any ideas on how to fix this?