I would like to inform you that you can use maximum 6 Readers and 6 computerswith one ID.
Now in order to fis the problem "User Not Activated" you can try following steps.
Solution 2) 1) Open Digital Editions.
2) Connect the Reader and open it.
3) Press the keys Ctrl + Shift + E on your keyboard.
4) Now unplug the Reader and replug it.
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 one or two folders 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.
I hope this will work for you!!!!
Yes, you can have up to six devices connected to one copy of ADE.
What I'm reading between the lines is that you may not have registered the
new Nook with B&N yet, and are trying to use it with ADE. Once you get it
registered with B&N, then you can add it to ADE as an authorized reader. I
have four ereaders now, and three of them are authorized to my copy of ADE.
One is authorized to my wife's.