Why is iframe not displaying on wordpress site?

Question

JavaScript

Hello! I am trying to install instagram widget from inwidget.ru website .
Locally everything works, the iframe displays the instagram page as it should. But when I put the wordpress engine on the host, it started to display only the main page. And that is not a page, but a header. What are the reasons why this might be so.

P.s. the instagram page is inserted like this:

<iframe src='/inwidget/index.php?toolbar=false' scrolling='no' frameborder='no' style='border:none;width:260px;height:320px;overflow:hidden;'></iframe>