1.How to do when the device is malfunctioning, like fail to boot, no sound when playing?

A: Here is a video FAQ to introduce resetting Q3:

Try to reset the Q3, or use another charger or data cable to charge it.

【Fail to turn on after a long-time of inactivity】
It is recommended to charge the Q3 with a low current charger, such as a computer or 5V/0.5A one.

【Reset】
Long press the GAIN button for 15 seconds until the RGB light (at the volume knob) goes out for 0.5s. The reset is completed.