Troubleshooting: Why am I getting no audio input on macOS Mojave?
Sound Studio requires microphone access for audio input, and you may have accidentally denied microphone access to Sound Studio. Granting microphone access is a new security feature in Mojave.
To grant microphone access permission, go to System Preferences > Security & Privacy. Click on Microphone in the left pane and then check the box for Sound Studio to allow access.