Sitemap configuration and actual generation
Compare configured file path and public URL of the store sitemap. Also check permissions and delivery by the upstream server.
Under Marketing › SEO & Search › Site Map, check the generated file and its path as well as the associated store context. The configuration and the last successful rebuild are different things.
Where to check the setting in Magento
Under Marketing → SEO & Search → Site Map, check the sitemap assignment to the Store View. Check the creation time, file path and accessibility of the registered products. In the case of automatic generation, the responsible cron run must also work.
Example of this specific finding
Illustrative control case: The sitemap index provides 200, but a partial sitemap linked to it provides a login page. The successful index retrieval is not sufficient as proof.
follow-up audit in Magento
After a product change, create a new file or check the schedule. Compare the public sitemap with active product status and reachable target URLs.
Retrieve index and any relevant part file as an unlogged client. Check the status, XML content and retrieval of these URLs separately.
Derogations and scope
An HTML error page with status 200 is not a valid XML sitemap. Even successful compression must be delivered correctly.
Reference: Magento Open Source or Adobe Commerce with classic storefront. Consider store views and extensions; other storefront architectures have their own configurations.
Classify the general error
Definition, system-independent causes and further correction examples: Retrieve sitemap index and individual files separately