Hm, that's odd. Sorry for that.
Please try to reset your old password. To do so, please open the app and go to "Settings" - "Profile" - "Log in". Enter your email address and click "Forgot your password" and we will send you a new password to this address.
If this does not work, please click "Report new problem" and tell us, how you try to register and which email address you are using for that. We try to solve your problem as quickly as possible.