You have already registered for our service with another username, to which your personal data is attached. You can register for the service with your personal information only once, which is why you have received the message. This is often due to the incorrect spelling of the school email (service sees addresses as different emails) or your own personal email. You can register for Frank with any email. Instead of registering again to the service, try logging in with your other emails. You can reset the password from "Forgot your password?" link.
If you don't remember the original username, send us a message at info@frank.fi. In order for us to find the original username, you must include your date of birth, full name and institution in the message. Also attach to the message the email you want to use for login in the future.