I wrote to the seller (Shanling Official on Aliexpress), he sent me recommendations for recovery and none of them helped.
The recommendations were as follows:
"When you encounter a situation where the product cannot be turned on or charged, please try the following methods to solve it:
1. Reset it.
2. Try to replace other charging heads or charging cables
3. The battery of your machine may be in an over-discharged state and requires low-current trickle charging. Therefore, it is recommended to connect a computer and other low-current charging equipment to charge the machine for more than two hours before checking whether it can be turned on.
4. The above does not work, you can try to let the machine stand for two to three days, and then recharge to see if it can recover. Because sometimes it may be that the machine is stuck, and it can be restored to normal after the battery is powered off."
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I tried all methods, except for number 1, because the instructions do not provide a way to reset the device settings (Hard Reset).
1. There is no way to do it.
2. I tried to charge from 4 different charging sources and 6 different USB-A to USB-C cables.
3. Charged within 7-8 hours from a laptop (USB 2.0) - Does not help.
4. A week was without use - Does not help.
All of the above methods did not help.
The electronics repair service center was diagnosed through a special USB tester.
I was told that the headset takes current from charging (see photo), but the device's battery does not charge - this is a hardware problem.
The device can operate for less than 1 minute from the battery on the residual charge and turn off. This is a defective battery.
Still waiting for a response from the seller. Hope for warranty service.
Shanling devices (UP4, MW200) for some reason cannot work with PowerDelivery chargers and, accordingly, do not charge via cable TypeC to TypeC.