1. Check whether the USB debugging function is turned on in the phone settings. Go to Settings > About phone > Android version. Click 'Build Number' continuously. After 'You are now in developer mode' appears, go to Settings > System > Developer options > USB debugging to enable USB debugging.
2. If the phone is charging properly and the USB port is working, reinsert the USB cable and select 'File transfer' for ' Use USB for'.
3. If the computer can't recognise 'Use USB for' and have selected 'File transfer', restart your phone and computer and try to connect again.
4. Change the USB cable, ensure that both the phone and computer USB ports are working properly to rule out any issues with the cable connector and USB ports.
5. If the computer has the phone drivers installed and a new device prompt appears when it's connected, it's usually a driver issue. In this case, reinstall the drivers.
6. Back up your data and restore the phone to factory settings.
If the issue persists, please contact our Customer Support for further assistance.