Q: Photo Book Pages

It will be hard to get the book printed by Apple at all. Apple announced that print products will no longer be supported for Aperture and iPhoto after the end of the month.

How are you trying to add pages?  It is still working for me when I use the "+" button below the pages browser.

Have you tested, uf you can add pages to a book, if you create anew book or use a different library?  The book may have a corruption or the Aperture library may need repairing.