Try pairing with the mobile using the steps mentioned, if this doesn't work proceed with the next step:

1. Open BT Settings in Mobile Phone

2. Turn ON the Bluetooth

3. Make sure your mobile and the Bluetooth headphone are within 1-meter range

4. Hold down the multifunction button on Bluetooth headphone for about 3 seconds until White LED Flashes 

5. You'll see the LED light starts flashing White continuously indicating that they are in pairing mode 

6. Select Tune Sport 2

Once successfully paired, the LED light will flash White  slowly