I have a fully paid up Prime account, but get a 'there was an error borrowing this title' message on my Fire HE when I try to read a Prime book on it.
It works ok on my S8 and will allow me to read them on my Fire once I've borrowed them on that. Why can't I borrow them straight from the Fire?
"An error" could mean a number of different things. As a result I would suggest you speak to Customer Service for a speedy resolution.