A solution when One side of Apple's AirPods doesn't make any Sound.

If you take the AirPods out of the case and put it in your ear, it sometimes doesn't make any sound. In particular, there are cases where only one side is taken out and heard, or both sides are taken out, but one side is not heard. At this time, you don't have to cancel Bluetooth or register for initialization. 

How to solve the problem of one side of Apple's AirPods being silent.

The way to do it is, just tap the AirPods that don't come out on your ear. After tapping, you can hear the sound when you connect to the AirPod, which connects to the cell phone within 1-2 seconds. 

This seems to be a bug that does not activate because it does not recognize that the AirPods were taken out of the case. At this time, when you tap on the AirPods, the user plays the role of giving commands such as the next song to play. At this time, the AirPods are recognized as being taken out immediately, and it seems to be activated and connected. 

(Tap to the left and right of the AirPods to set each previous song or playback function.)  AirPods Pro is probably a poster type, so I think you can press it instead of tapping it.)

Another method when not resolved by the above method

What if it doesn't connect even after the sound of AirPods connecting? First, open the control center, touch the media player 3D or long, and touch the airplay, and the AirPod will appear there. If you touch it, it will be solved.

A special case where the above method doesn't work again. 

However, for Spotify and multi-device playback apps, strangely, the AirPod itself appears to be connected to the iPhone, and you can control the iPhone with the AirPods, but sometimes the sound comes out on the iPhone. In this case, you can close the app and restart Bluetooth. If this doesn't work, the iPhone needs to be restarted as a last resort. 

A solution for Android phone users.

People who use both Android smartphones and Apple AirPods can use the same solution as above.