I've looked at the Directory page, it appears to be built via a custom page builder of some sort. Some page builders use custom fields to store their data, including the post data as well. On the General Options -> Sources panel I have enabled the search in all custom fields option, now it will return the directory page properly if you search any of the content there.
Returning the individual elements on that page is not possible however, because they are not separate objects (like post types or taxonomy terms). The items there should be post types or terms for the plugin to be able return them – because currently this is only stored as a single page in the database. In the database the content of that page is seen as one post meta for the directory page. I usually recommend creating and using a post type to separate and store information.Best,
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