In the DevTool of your web browser you have this kind of message because you’ve been to the url (or a completely different domain like that contains an HTML page which includes an iframe of

This message means that the URL returned a X-Frame-Options header set to ‘DENY’, that simply means that the webserver that hosts refuses that you include it in another website (with same domain or not).

If you can manage configuration of the webserver where is hosted just add these two headers. For instance in apache webserver, include these two headers in the virtualHost of

Header set X-Frame-Options: "ALLOW-FROM"
Header set Content-Security-Policy "frame-ancestors 'self';"

The first line is for compatibility with old web browsers because as explained here:

Note: The Content-Security-Policy HTTP header has a frame-ancestors directive which obsoletes this header for supporting browsers.”