Solution:
1. If the App upgrade fails, please click to retry and upgrade again.
2. After the band connects to the App, pull down the synchronization data in the "State" again, which will trigger the firmware upgrade of the band again.
3. Restart the Bluetooth of the phone, and upgrade after opening the App again.
4. Check whether the power of the band is lower than 10%. If the power is lower than 10%, it cannot be upgraded