Please refer to the following instructions:
Kindly be reminded that the compatibility of Catalina onward is still under development at the moment. If your Mac OS is Catalina onward, you can try using Kext Utility for Mac to see if it helps.
- Download XDisplay Agent for Mac. (http://www.splashtop.com/wiredxdisplay)
- Wired plug your Android or iOS devices to your Mac, make sure your device is detected, and open the Wired XDisplay app. If your device isn't detected, please try using a different cable.
- Click on the WiredXDisplay on the menu bar > Preferences > Arrangement
Make sure that the mirror display is unticked.