Qt breaks WebBrowser control somehow (Ajax is not working)

Windows 10.

I have 2 applications using the same C++ library which creates WebBrowser control (Internet Explorer based control). It does not use Qt, only WinAPI.

First application is raw WinAPI based C++ application which does not use Qt.

A second one is Qt 5.9.2 widgets based C++ application.

In both applications I try to open the following URL: https://vi.infcdn.net/test.html.

The problem is that in my first app this web page works as expected. But in my Qt based app it does not work. Ajax is not working on it.

I've also tried webbrowser example from Active Qt examples folder. (http://doc.qt.io/qt-5/activeqt-activeqt-webbrowser-example.html). It's not working here too.