Book App on Mac (The operation couldn’t be completed. (BKBookKitFoundationErrorDomain error -1010.)

I am trying to add an audiobook to my Mac Books App. It is an audiobook I bought from the iTunes bookstore in 2020 and has an .m4b format. As I understand I am no longer able to re-download it from the iTunes Bookstore. The audiobook has been successfully downloaded onto the Book app on my iPad and iPhone, but when I try to download onto my Mac I get the message The operation couldn’t be completed. (BKBookKitFoundationErrorDomain error -1010.). I have an iMac Retina 5K 27" Late 2014 running Big Sur. I have recently been re-organising my Books app content and, despite the fact I made a copy of the audiobook onto my hard drive (which I do for all my purchases as a backup) I am now unable to add it to the Books App. Any advice most welcome. I