As recently as 3 days ago, I believe this was working correctly: when I clicked on categories, it would display a list of posts in that category. Right now, when I click on a category, it displays only the most recent post from that category. The other posts are still there and have not been deleted, but you can't see them. I have been able to access them from pins on Pinterest.
The only change I have made to my site since Wednesday (when I was using that feature to pin posts to Pinterest) was to install the plug-in "WordPress SEO". I'm not sure how that would affect it, but I mention it just in case.
I can't find any settings that allow you to choose what is displayed when you click on categories. Am I missing something? Can anyone help me figure out what happened and how to get it back to normal?