AirPods does not automatically connected to my iDevice
Though my AirPods connected to my iPhone before, once I disconnected it and reconnect it again, it will atomically connect to the iPhone but does not switch to AirPods automatically. My speakers will work instead of AirPods, I have to manually switch the sound source to AirPods manually, and this is the problem. (Low battery mode is not the reason why it does not work as my friend does not have to switch it manually like I do.)
On your iPhone, iPad, or iPod touch, go to Settings
Reset your AirPods
Reconnect your AirPods