You probably have multiple logins for my.presonus.com, if you have previously logged in using the social media buttons, a new account would have been created for that email address if it was different than a previous login. For example if the email address that's associated with your facebook, google or linked in account were all different you'd end up with 3 different accounts. Try logging into http://my.presonus.com
with a different email address and/or attempt password recovery if you don't remember your password.
If you're not sure, then log a support ticket at http://my.presonus.com
and provide us with your Studio One key and we can find the account your software is registered with.