One of my projects for work is supporting ebook software (specifically a platform of interactive ebooks that primarily offers medical texts and other textbooks).
This is an example of a type of email I see multiple times a day:
'I am trying to redeem a code and it does not work!, is a new book the I got a week ago.'
No code. No title of the book. Just that.
And about half of these people will, when I have to push back for info, cry about it 'taking so long' (we manage to reply to most people within 24 hours) or 'being so difficult.'
More fun: 9 times out of 10, they're just ignoring the place on the page the code is on that says 'Go to this specific link to redeem your book.'