Some solutions if you can’t see your XML sitemap or you get this error from Google Search Console “Your file appears to be an HTML page”:
- exclude XML and XSL files from your caching plugins
- exclude XML and XSL files from Weglot plugin
- exclude XML and XSL files from your CDN (Content Delivery Network)
- update Really Simple SSL plugin to the latest release
- enable define( ‘WP_DEBUG’, true ); in your wp-config.php to see the error
