Iveth,
Sorry for the delay. I just tested quite a bit on your site, but was unsuccesful in finding the problem for not logging in.
One thing I did notice is that even if I try to login on the JomSocial home page using the Joomla credentials you sent me, I'm not actually logged into the site. Something seems to be preventing any sort of logins on the front end, from what I can tell, and JFBConnect is simply affected by the same problem. Unfortunately, I have no idea what is causing the problem, but hopefully knowing that it happens to standard Joomla accounts and using JomSocial as well will help narrow things down.
Please let me know if you determine the cause or if you need more help. We'll gladly do whatever we can, but from what I can see, this is not an issue with JFBConnect or the SCLogin module directly.
Thanks,
Alex