The Yoast SEO for WordPress plugin is able to detect content from both the text and visual mode of your WordPress native editor. In addition, the plugin is also able to detect the content while using some other page builder plugins. Currently, not all the page builder plugins and themes are supported, nor is the plugin fully able to detect and highlight the content in some cases while using the page builder. To get the best results, you’ll need to use the WordPress default visual editor.
Can you let us know if you are using a page builder plugin such as Visual Composer, Site Origin, Beaver Builder etc to create your page’s content? The text highlight feature sometimes does not work correctly if you are using some kinds of visual page builders, as they can cause the page’s content to not be accessible to the plugin due to it being created outside the functions of the standard WordPress page editor. If this is the case, currently the only workaround to this currently is to create the content from within the standard WordPress editor.
If you are using a plugin or theme that doesn’t send their content to our page analysis, please reach out to the developer and ask them about adding the functionality to their code. This KB article will help them with the implementation: Can I add data to the page analysis? https://kb.yoast.com/kb/can-i-add-data-to-the-page-analysis/
That being said, while our plugin isn’t able to detect all your text blocks and shows an incorrect analysis report, this doesn’t mean that search engines won’t be able to parse them. Our content analysis is just to validate the content of your website and doesn’t really affect how search engines crawl and index your site.=