I'm having trouble with Digital Editions on my Nook Color

I downloaded Brad Thor Collectors Edition #1 and #2 to Digital Editions on my Windows 10 Laptop.  Then I copied both book sets to my Nook Color,  When I try to open either on the Nook Color I get an Error Dialog "Sorry, cannot open this book".  I then downloaded another different e-book from the same library and opened it successfully.  I can open either collection directly in Digital editions on my computer so I know the download from the library is good.  Please help.