Hi WayneWWW,
The problem is solved!
The problem was, we flashed the board using custom rootfs using downloaded sample rootfs. And set the username and passsword using l4t_create_default_user.sh.
When we tried to install and flash the board using Nvidia SDK Manager and configure it using connecting to HDMI display. Also enabling the Bluetooth audio explained in forum(link), now the bluetooth working fine.