Before pairing your earbuds please ensure they are 100% charged 

To pair: 

1- Open the charging case.
2-Turn on the Bluetooth of your device.
 3- Select Add Device and from the list of devices, select Noise Air buds 2

b) Set your Mobile Phone to Airplane Mode and then again set to normal mode, mobile's BT working will back to normal if any small bug is there with BT's working. If succeed, then ok otherwise move to step- c

c) Restart mobile phone to refresh Mobile Phone's working and Mobile RF will also back to normal.
If Restart is not available then Power OFF and ON the Mobile Phone.
 Now again try and follow the pairing process.

d) If device's LED shows pairing mode and its name is not visible in BT search result interface, Try to refresh BT search result in Mobile Phone.
If still can't see the device name then try pairing process with different mobile phone
 

Note: If device is working fine with other Mobile Phone then there are chances that issues might be with the previous Mobile Phone as well.

e) RESET the device 

1- Remove device name from Bluetooth Interface
2- Open the charging case and let the buds stay in
3- Press and hold the reset button for 7 seconds
 4- the LED on the buds will blink 5 times indicating the buds have been RESET then repeat the pairing process. 

f) If above mentioned 4 steps doesn't work then please check if LED is there or not. if no LED then The device might be out of battery.
 

Follow the instructions given in UM to charge the device.