Most microphone and video camera problems are caused by your operating system, browser or device settings.
If you are having problems, try the following:
Close all browser tabs and restart your computer and browser.
Make sure all other software that uses your camera or microphone (Skype, Zoom, etc.) is closed and not running in the background. Try closing all non-essential processes if you know how to do so.
Check your browser's permission settings:
There is a guide here for Chrome: https://support.google.com/chrome/answer/2693767?co=GENIE.Platform%3DDesktop&hl=en
There is a guide here for Safari: https://support.apple.com/en-gb/guide/safari/ibrwe2159f50/mac
Once you have changed your settings, hard refresh the browser:
Windows (Chrome) → Press Ctrl + F5
Mac (Chrome, Safari) → Press Command (⌘) + Shift + R
Check that your operating system has the correct microphone, camera and speaker selected.