I communicated with Nook support and share the serial number. Their feedback was "my Nook is disabled, that's why it is not registering..." usually the device is disabled for lost, stolen etc cases. But I told that the device was purchased from bestbuy.com and it reached to me with intact packet. Also I have invoice of it. But they told me to talk to Bestbuy.com.
Later, I called to Nook's hotline asked that where the issue is related to the location from where I'm trying to use it. Feedback was - Nook is useable only from USA and UK having a valid credit card. It cannot be used from Bangladesh.
Now, what should I do to make it workable from Bangladesh?