Based on your previous posts, I'd check:
1. That the site's /includes/configure.php references the correct HTTP_SERVER and HTTPS_SERVER (
https://www.mydomain.com or
https://mydomain.com). Both should be the same and both should be https:// based.
2. That the site's .htaccess file is (like @dbltoe identified above) performing a redirect to the 'correct' server, as identified in the configure.php.
3. Ensure that the site's robots.txt points the search engines to the generated sitemap.xml file, again using the 'correct' server.
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