Sorry to hear of the problem you are having.
I have tested it on my test site and it’s working fine for me as displayed in the attached screenshots.
Please make sure your web host is not restricting your site to connect to shufflehound.com
No there isn’t any manual demo.
Have you contacted your web host to make sure that your web host is not restricting your site to connect to shufflehound.com ?
Please make sure you are using latest version of PHP on your server by referring the information provided in the following pages.