All students receive temporary access to eBooks in Canvas for the first 14 days of class. If the student has not initiated a login via Canvas after this period, it is possible they were not provisioned a full license. Try logging in through Canvas, and then resuming access outside of Canvas. 

Additionally when accessing some access codes/courseware, the publisher may require you to register your code. If the student skips this step and continues without registration, it may prompt their system to give a 14 day temporary access to the student instead of the purchased materials through LMP.