Open an online mic test in Safari or Chrome and click Allow when prompted. If the waveform moves when you speak, your mic hardware works. You can also test natively: go to System Settings > Sound > Input, select your microphone, and watch the input level meter while you talk. If the meter doesn't move, raise the input volume slider. For app-specific issues, check System Settings > Privacy & Security > Microphone and make sure your browser and meeting apps are toggled on. After changing permissions, quit and reopen the app. If using a USB or Bluetooth mic, disconnect and reconnect it so macOS re-detects the device.