Structured knowledge is extra on to a page's HTML markup. Search engines like yahoo use structured knowledge to generate rich snippets, that happen to be tiny pieces of data that could then show up in search engine results. The problem could be brought on by possibly spammy information or spammy https://addons.prestashop.com/pt/seo-referenciamento-natural/31857-rich-snippets-automaticos-json-ld-opengraph-seo.html