The most common reasons for sites not working withing iframes is the X-Frame-Options: SAMEORIGIN header returned by the server. This is done intentionally to prevents all other sites from embedding such a site (see also a more detailed description of this header here: X-Frame-Options - HTTP | MDN)
I’m not sure if this is the problem also in your case, you can verify it by looking for errors in the Network tab for Google Chrome developer tools (F12).