There are two possible causes: 1. The internal charging circuit is faulty. 2. The battery is faulty.
The portable WiFi router will inevitably be bumped during use. If there is virtual welding in the internal circuit, it is likely to cause the solder joint to fall off and thus cannot be charged. It is also possible that the electronic components in the circuit are damaged, resulting in a failure to charge. At this time, you can find a professional to open it for inspection.
It may be the fault caused by the damage of the Bluetooth headset battery, in which case you can only bring the Bluetooth headset and its purchase invoice to the nearby maintenance network for detection, repair or replacement of a new battery.