Here is a step to try on your chromebook.
Go here - https://meet.google.com/landing
Click on the icon that this arrow is pointing to, and Reset Permissions.
Then open a new meeting by going to meet.google.com. Click new meeting - start an instant meeting. If your camera or microphone don't come on, then click the icons in the meeting -
And you will be asked to allow the camera and allow the microphone.