I am having the same problem- I have not encountered this problem until today. I've successfully downloaded many ePub books but now Adobe is not recognizing my Nook.
In order to fix the problem you may follow steps as given below.
Solution 1) 1) Open Digital Editions.
2) Connect the Reader
5) There you will find a new drive created similar to C or D drive under "My computer".
6) Open the Readers Drive and you will find a folder with name "adobe.digital.editions".
7) Delete this folder and plug off and re plug in the Reader.
8) Authorize Reader from the same Adobe ID which you used to Authorize Adobe Digital Editions.
.. 9) Now try to transfer books to your Reader
Solution 2) Modify the manifest.xml file located in C:\Usres\Username\My Documents\My Digital Editions:
1) Quit Digital Editions
2) Make a backup copy of the manifest.xml (call it something like manifest.good)
3) Open manifest.xml in notepad
4) It will appears as one big long line of xml, and you are looking for a tag called start at the begginning of this
and select until you the end of the tag that looks called </de:deviceID>
5) If you have attached more than one Reader there may be multiple of these. Delete all of them to make sure.
6) Save the file (manifest.xml) and quit out of notepad
7) Ensure you have the Reader plugged in
8) Launch Digital Editions
9) The Device Setup Assitant should come up.
a) Do NOT click on the "Don't ask again for this device" checkbox.
b) Do click on the "Authorize Device" button.
I hope this will help you.
Thank you so much. Your first solution worked just fine. I appreciate your help.
Follow what rizwan suggested for me to do. It worked. Good luck to you.
Good to know that ur problem has been fixed.
All the best..