[Plugin: WordPress SEO by Yoast] Google Webmaster cannot find sitemap

The bug fix of Joost to add header( 'HTTP/1.1 200 OK' ); seems not to be a solution. Also to remove only this single header line as posted in https://www.ads-software.com/support/topic/patch-included-sitemaps-xml-parser-complains-about-invalid-characters did not help me.

Removing all header() calls in that function did solve the problem. As there are other posts which complain about problems with “headers already sent” errors, I suspect there is somewhere or sometimes HTML output in the plugin in before.

I think the target should be to prevent the 404 in the first place instead of overwriting it later as this seems too dependent on the environment. https://www.php.net/manual/en/function.header.php mentions a different notation for FastCGI in the parameter description.

I could create a reproducable error behaviour with sitemaps.

See post https://www.ads-software.com/support/topic/sitemap-fails-only-after-reenabling-seo-plugin.

Removing all headers in function output() did not solve the problem anyway.