I changed themse to Twenty Seventeen and the posts showed up.

Your theme is the problem

What can I do about the theme? I purchased it.

– For pro or commercial product support please contact the author directly on their site.
– As the author is aware, commercial products are not supported in these forums. As you are their customer I am sure they will have no problem supporting you there.
– Also, forum volunteers are not given access to commercial products, so they would not know why your commercial theme or plugin is not working properly.