Nook not showing on ADE screen?

The book I have downloaded from my local public library appears on the ADE screen, but the Nook icon does not appear...so I cannot transfer the book to my Nook.

I have not made any changes to the OS (Windows 7) and ADE worked fine with the Nook last time I tried to transfer a book.  Others appear to be having a similar problem but no one has provided a solution.