This happens because the student has already registered their license key, and account for this license key's material already exists. Simply advise your student to log in to their existing account on Student Materials Portal - https://students.berlitzdigital.com with their registered email.
Use case: Student goes to https://berlitzdigital.com and enters their license key. They get below error message and a re-direct/ prompt to log in to their existing account on Student Materials Portal with their registered email.
