As of September 7, the official NOOK forum at Barnes and Noble is shutting down. From the posts on the site, it seemed that posting activity had dwindled to a small number of posts. Users of the forum received an email on the closure.
While the forum may be closing, assistance is still available from Barnes and Noble. According to the post,
Though the forums will no longer be around, we’ll still be here to answer all your support questions at https://help.barnesandnoble.com/ and on social media at the following links:
If you are looking for another forum, there is still an active community of Nook users at NOOKBoards.