google-xml-sitemaps

This is probably due to empty lines inside your custom php files. Try checking every php file you edited for empty lines after the ?> closing tag: the tag should be the last character of any file.

Missing XML tag in the Sitemap

First of all, you can use Stack Overflow in Russian, there is a WordPress tag. Concerning your question, it seems everything is OK with your sitemap. Yoast SEO generates index sitemap mentioned in your question and several sitemaps for pages, posts, taxonomies, products in WooCommerce etc. You can check this sitemap in Google Search Console, … Read more