I can take a look. Can you please fix the Javascript error from your side also? This is not from the plugin. It is something added by a google tag manager! 

And have you removed the settings I told you? 

If the first Javascript error causes all Javascript to stop then it does not matter which url you use later...

You can contact me here: http://www.tinywebgallery.com/en/about.php please don't share any credentials here.

Please check my post before. There is a Javascript error - not related to the iframe plugin. This can cause that all stuff after that fails.

This is why I told you to remove hide_page_until_loaded_external="true" and hide_content_until_iframe_color="#ffffff" .

You can try 10 urls. If you don't fix your Javascript error the code after that is not executed. The "un"-hidding is done by Javascript. If you remove the 2 things I wrote the iframe is not hidden.

Best regards,

Michael