Hello Tikaram, and thanks for the quick response.
I am familiar with setting featured images in posts and pages, and I thought that might be the issue, so I checked that before I posted my question here. When I previewed the posts in question, no images were displayed. I just checked those posts again, and sure enough, when I expanded the “Featured Image” option, the images that disappeared are in fact the featured images in the Services section that had disappeared. So now I set featured images for the pages I chose to put in Services, and it works. However, when you set a featured image in a post or page, is that image not supposed to display in the post or page when you preview them or visit the site and go to those posts/pages? That’s why I didn’t think that was the issue…the featured image does not display in the post or page itself. That behaviour is unlike any other WordPress install I have worked with.