There are a couple of reasons why a browser might not be able to access the camera:
- The browser runs in the incognito / anonymous / private mode. Browsers usually forbid access to the camera in that case.
- The access to the camera has been disabled in general. In Chrome, you can change these settings as follows: Go toPreferences, Settings, Show advanced settings, Privacy, Content settings, Media, and enable "Ask when a site requires access to your camera and microphone".