Not sure if I had the same problem, but try to open this page: http://www.facebook.com/username , go back to gwibber and use your username instead of your email when you login to your account. After that the Add button appeared for me.
Not sure if I had the same problem, but try to open this page: http:// www.facebook. com/username , go back to gwibber and use your username instead of your email when you login to your account. After that the Add button appeared for me.