There can be a second layer of audio-enhancements from the computer manufacturer, e.g. MaxxAudio.
Or Skype/Zoom may have a hold on your microphone.
It’s definitely not Audacity to blame : it’s not capable of applying (noise-gate) effects in real-time.
If you try Audacity’s competitor, OCENaudio, and the problem persists then that’s proof Audacity is not to blame.