After logging in, you can activate new learning materials with an activation code. If, after typing the code, you get the message that the code is already in use, this is the case. This may be because you have borrowed or bought a book from someone from which the code has already been activated.
Activation codes can only be used once.
Nevertheless, if you believe you have a new code, please contact customer service. Mail a picture of the code to: nt2@boom.nl.