Check Mac system settings - https://support.apple.com/en-gb/guide/mac-help/control-access-to-your-microphone-on-mac-mchla1b1e1fe/mac

1. On your Mac, choose Apple menu > System Preferences, click Security & Privacy, then click Privacy.
2. Click Camera.
3. Select the tickbox next to an app to allow it to access the camera. Deselect the tickbox to turn off access for that app.
4. Follow the same process for your microphone

If you don't see the Camera/Microphone setting in the Privacy section, please update your Mac OS to the latest version - https://support.apple.com/en-gb/guide/mac-help/mchlpx1065/mac

Check further steps based on which browser you are using such as Chrome help. If you'r using Safari, they do not have the latest camera technology. Please use Chrome or the new Microsoft Edge

If you have multiple audio devices connected to your Mac, it might sometimes not select the one you are trying to use. Here's how you can change those settings:

1. Open your System Preferences
2. Click on "Sound"
3. Click the "Input" option
4. Here you will see a list of your audio input devices - select the device you are wanting to use.