Sounds like a computer issue. My laptop has a physical 'Mute' switch and also mic level control in 'Settings'. This also allows selection between internal and external Mic.
------------- Two drifters off to see the world.
I'm tired of reality, so I'm off to look for a good fantasy.
Not sure whether you're using Whatsapp on a PC or Android phone. You don't say. Try going into settings, then permissions and give the app permission to use the mic. Most apps need permission to use and access certain areas and may be switched off by default.