If you encounter a situation where Systemwide is receiving seemingly low or no input signal at all, it's worth checking the following settings:
In Spotlight search, type "Audio MIDI Setup", open it and click on Sonarworks Systemwide device. There make sure that all three volume faders are maxed out (see the image below)
If you are still not getting any signal from Systemwide, please make sure that Systemwide isn't muted in your Mac System Preferences > Sound settings Output tab (image below)
If you are on MacOS 10.14 Mojave, please also make sure that you have allowed microphone access to Sonarworks software. You can read more about it here.