Gallery Picture Size?

Since updating to the current version of Word Press, I notice that images loaded into a gallery, and uploaded in bulk, are no longer clickable. Previously the small images could be clicked to view the larger picture. As in this older post

Now, after the update, clicking the small image reverts to the website. See in this one https://gleanings.org/?p=7902 I can see how to set the default for pictures to enlarge when loading them one by one in the body of the post, but I’m specifically looking for a way to upload a gallery and have the gallery thumbnails enlarge when clicked on.
TIA for your help!