eBay has clear guidelines
about that, for years.
Examples of digitally delivered goods that can't be advertised on eBay: (...)
eBooks you don't own the copyright to and aren't authorized to resell by the owner, the owner’s authorized agent, or the law
If you list eBooks in a category other than the Everything Else category, you need to:
Send the eBook by postal mail.
Which is kinda bizarre. But again, them's the rules.