Why trying to let the browser to access webcam an error is detected?
If you experiment a warning and your webcam doesn't show up after clicking and allowing browser to access cam, the problem could regard the hardware itself.
If the videochat box for your video shows the message below this means that probably the webcam is used by another application in the system and it's currently busy. Try to ensure that it's correctly configured and close any other application that could have access to webcam.
To ensure that your webcam is working you can test it using another external application different from the browser if you have it installed on pc. Doing this test you can ensure that hardware is working and the driver is correctly installed.