Hello,
Thank you for contacting Rank Math and bringing your concern to our attention.
The issue you are seeing is caused by an XML declaration error on your sitemap. This means that there is some extra content or whitespace before the XML declaration in your sitemap file. This can make your sitemap invalid and unreadable by search engines.
The most common reason for this error is a whitespace in your theme code, such as a blank line or space in your wp-config.php file or your theme’s functions.php file. This can happen when you edit these files manually or use a plugin or theme that modifies them.
To fix this error, you need to find and remove the whitespace from your theme code. You can follow this guide to troubleshoot and resolve this issue: https://rankmath.com/kb/fix-sitemap-issues/#xml-text-declaration
If the issue persists, you can also use this script to automatically fix this error: https://wejn.org/stuff/wejnswpwhitespacefix.php.html
Looking forward to helping you.
