1, the charger may be damaged, you can try to change a charger to reconnect.
2. The small battery in the Bluetooth is dormant or broken. (Can be disassembled with a regulated power supply to try to activate)
3, headset memory connection times are full.
4, the battery is in poor contact, or the protection board is damaged, you can check it with a voltmeter, or it may be the internal line is damaged.