- (Edited)
Please follow the below steps:
1. Go to Settings>About Phone>Software Info>Build Number and tap 7 times. After “You are in developer mode” appears, please turn on USB debugging in Setting> System>Developer Options>USB Debugging.
2. If the phone is charging, unplug and re-plug the cable. If “USB for Transfer Files” does not show up on the phone, please restart the phone and try again.