Arya Black

I have a problem. When I want to start playing....for example Hexxit, launcher write: Your username or password is invalid. I write username and pasword same, like I use to log into the site technicpack.net. But it always write that name or password is invalid. I have confirmed the email account and key so I do not know what the problem is. Maybe because the account on page isn't account for launcher? In that case, where do I sign up so I can play? Thank you :)