Never deny access to your coursework for any reason.
Why am I paying for a textbook to which I have access? Under no circumstances should I ever receive a message saying "you cannot access your coursework due to an error on our end."
I paid almost $200 for this textbook, and I have limited time to access the coursework anyway (I work full-time).
This is beyond substandard; it's unheard of in this business. If you want to highlight how digital textbooks enhance the student/customer experience, you had darn well better ensure your customers/students have FULL-TIME access to said coursework.
Again, under no circumstances should I ever receive this appalling and egregious error message. I expect this to be fixed immediately, and I would like a refund, as what I paid for was not delivered.