Is this registration with social network credentials or when you hit the Register button on the SCLogin module? If it's the register button, SCLogin is simply redirecting the registration to the extension selected in the "Registration Component" setting and we wouldn't be throwing that error. I tried logging in via FB credentials on your site, and your application is still in development mode, so I an unable to test. Either way, please provide more details on the steps to reproduce your problem.
You need set to Register ("Kayit" in Turkish) and as soon as you have new screen. If you cantinue entering your information here on the registration page, you will fail to register due to this error. see attached screen shot.
As I mentioned the component that you're attempting to register with is not JFBConnect or SCLogin. It is the Joomla standard users component com_users. We have no control over creating a user on this screen with standard Joomla users. Even just going to the same URL without going through SCLogin, you'll receive the same error about the password.
Just to verify, please disable all JFBConnect plugins and re-visit the registration page again to check to see if the error is still there.