Can you to go to your macOS Settings, to the Privacy & Security tab, then check under Files & Folders that you haven't restricted MixEmergency's access to your main drive? This is the most likely cause of this.
If it's still not working then can you please email me (to: support@inklen.com) your MixEmergency log file? You can find it at the following path:
~/Movies/MixEmergency/MixEmergency.log
(where ~ is your home/user folder)