Okay, the page has loaded so I've been able to take a look at it. I think you have two different sitemap plugins installed - or possibly your theme has a built-in sitemap capability of its own. It seems that the [sitemap] shortcode is activating both.
You can either disable the other sitemap plugin, or if it's part of your theme you can change the shortcode for this one.
To change the shortcode open the file named
atlas-html-sitemap-generator.php in the plugin folder. Line 63 reads:
add_shortcode( 'sitemap', 'dmac_html_sitemap' );
You can change the
'sitemap' bit to anything you like, e.g.
'my-sitemap'. Use the new shortcode and that should solve the problem.