If you don't see the audio bar moving under your video preview when joining a session, make sure your microphone isn't muted on your computer.
Check your microphone on Windows:
1. Right-click on your computer’s audio device icon (It can be found on lower right part of your desktop).
2. Click on Recording devices.
3. Right-click on your default microphone device (the default device will have a green checkmark) and then click on Properties.
4. Under properties, go to the Levels tab and see if your microphone is on mute. The speaker icon will be crossed out if the device is muted.
5. Click the speaker icon to unmute your microphone, then click OK.
Check your microphone on Mac:
1. Click the Apple in the upper-left corner, then choose System Preferences.
2. Click "Sound." Choose "Internal Devices," then click the appropriate mic. Make sure you see movement on the bars below and turn the volume slider up accordingly.
Look in the upper bar near the URL and locate the little speaker icon. Usually, there's a slash or red X over it if muted. Click and change accordingly.