This article seems to point to a class definition somewhere in the Theme that is lacking some of the possible entries that can be included in the class. I briefly looked at a few of the theme files and could not easily find the code snippets they are talking about but thought I’d raise the issue and see if you have a solution.
@gbishopdu-edu In the theme folder, go to content-extensions file located in theme folder->library folder->structure folder. Look for these functions cleanretina_theloop_for_page(), cleanretina_theloop_for_single(), cleanretina_theloop_for_archive() and related codes inside it and try to make the adjustment there.
.
.