You simply put in the extremely popular YoastSEO plugin. When clicking the on the sitemap XML hyperlink you uncover a 404 error on the web page that takes you to www.yourdomain.com/sitemap_index.xml
Earlier than you dig too deeply into the difficulty and begin to modify .htaccess or any code. Attempt to disable the XML plugin after which re-enable. More often than not it’ll repair the issue on a brand new set up.