Your template has the following line in it's CSS:
#jsn-master .modal {
position: static;
}
That's in the following file:
/templates/jsn_epic_pro/css/template.css
At line 1352
You'll need to comment that block out to prevent the conflict it's causing with our login modal.
I hope that helps, but if you need any more assistance, please let me know.
Finally, if you haven't already, please consider leaving a rating and review for SCLogin, or our support, on the Joomla Extension Directory. It certainly isn't required, but is very appreciated:
extensions.joomla.org/extensions/access-...authentication/24054
Thanks,
Alex