Why can't the Xiaomi Power Bank 20000 (Integrated Cable) charge the phone?

If the Xiaomi Power Bank 20000 (Integrated Cable) is left unused for an extended period when its battery is very low, it can cause abnormal voltage, resulting in the inability to charge a phone.
If the power bank is unable to charge, follow these steps to restore its functionality:
1. You need to connect the power bank to a power source using its original charging cable. Low-quality cables or damaged cables can not provide sufficient current to reactivate the battery;
2. You need to plug your phone into the power bank while it’s being recharged. Sometimes, charge the power bank while using it will help stabilize the voltage;
3. Then you should wait about 40 minutes to 2 hours to allow the power bank to charge uninterrupted. If the battery was deeply discharged, it will take time to regain enough voltage to function normally;
4. If the power bank still doesn’t work, unplug and reconnect the charging cable. Extend the charging time further, as some models require additional recovery time.