Why does my Bluetooth headset have no sound when Camera Guard Mac is running in the background?

The problem lies in how the Mac communicates with the headset.

Since the headset is selected as audio "input" and audio "output" in the Audio System Preferences, the microphone protection affects both. If the built-in microphone is manually selected as "input" in the Audio System Preferences, the protection still works with working headset sound.

Since version 3.7.6, Camera Guard can force to protect the built-in microphone. For this, "Force built-in microphone" should be checked in the settings.