I hadn’t heard of Nicepage before today but, if my Google search is correct, Nicepage is a page builder. Yoast SEO analyzes the default WordPress content areas like the title, URL, the main content box (WordPress editor). If you are adding your content through other plugin or theme content boxes (as most page builders do), Yoast SEO might not be able to detect it, by default.
In the past, we have tried to parse shortcodes and other content boxes with inferior results. Therefore, we opted to provide plugin and theme developers with an API that they can use to pass their content to our page analysis.
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 product. This developer article will help them with the implementation —?Can I add data to the page analysis?
With 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 to validate the content of your website and doesn’t really affect how search engines crawl and index your site.