Since MacOS Mojave 10.14 security and privacy protections now require the user to enable microphone access for Sonarworks software. After installing the Sonarworks software on macOS Mojave (or running it for the first time after updating to Mojave) you will be prompted by macOS to allow Systemwide's access to the microphone (see the image below). Please choose 'OK' to allow.
If you didn't get this pop-up window or you wish to change your permissions later, you can adjust your privacy settings manually by going to:
System Preferences → Security & Privacy → Privacy → Microphone → Reference 4 Systemwide
and clicking on the check box next to the Reference 4 Systemwide (or True-Fi) app (image below).
Please note that you need to 'click the lock to make changes' and enter your log-in details to adjust these settings.