The resolution for a 21-inch screen is much higher than for a 15-inch screen, so I'm guessing the resolution is too high for the webcam videos. Lowering the screen resolution should allow the webcam to work.
The information on Computing.Net is the opinions of its users. Such
opinions may not be accurate and they are to be used at your own risk.
Computing.Net cannot verify the validity of the statements made on this
site. Computing.Net and Compnet Ventures, LLC hereby disclaim all responsibility
and liability for the content of Computing.Net and its accuracy.