Exclude categories from search

Searches are executed by Google and not your WordPress site.
This plugin only displays the results that Google find, but this plugin has no impact on the results, it is the SEO plugin and Google responsibility.

Please check that your SEO plugin supports this functionality.

For example similar functions are described here:
https://yoast.com/articles/wordpress-seo/#noindexfollow

You can find more information about indenxing meta tags here, that prevent the page from appearing in Google Search:
https://support.google.com/webmasters/answer/93710?hl=en