If your website url starts with http:// it will not work. You can test your insecure website here. You should seriously consider getting a hosting account with ExelWebs that includes a free SSL certificate to improve your visitor experience and avoid the "Not Secure" warning in Chrome and Firefox.
This is not a tool for testing, it is really important that you do that on real devices. This instead is a tool for quick screenshots (for me) and to visually allow people to “get” what you mean in client meetings.