Inspecting the registration link on the button, it's pointing at "/index.php/en/component/users/?view=registration". When clicked that's being redirected to "index.php/en/component/users/?view=login". There's something on your site that's redirecting the link. If I type in "index.php?option=com_users&view=registration" myself and not from the SCLogin module, it's being redirected to the login view as well.
Please check that you don't have any aliases set up in extensions such as SH404. Verify that New User Registration is enabled in your Joomla Users parameters.
-Melissa