I’m frustrated

Can't register either of my two Wrox DotNetNuke books

I attempted to register my DotNetNuke Module Programming (ISBN 978-0-470-17116-5) and DotNetNuke Skinning and Design (ISBN 978-0-470-10963-2), but I got an error stating that "The following identifiers match no registrable product." Is there any way to register my print books so that I can upgrade them to ebooks?

Thanks in advance for your response
1 person has
this problem