Hello: Please use MP3 format for formatting, and try not to use computer format.
Press the back key for 8 seconds when starting the computer, and then you can clear all the contents on the disk, and then put the M6SL.ebn and resource.bin files of the upgrade package in at the same time, and disconnect the USB.
If it still can't be solved, it is recommended to consult the local Meizu certification store for after-sales service.