Here are the steps to troubleshoot a malfunctioning webcam:

1. Update your webcam drivers.
2. Check if your webcam is correctly plugged in and its cable is intact.
3. Make sure the privacy shutter is open.
4. Make sure the settings of the webcam are correct and its brightness and contrast are properly set.
5. Make sure your firewall and antivirus/antispyware software allows the webcam application.
6. Try uninstalling and reinstalling the webcam's driver and application.
7. Try a USB port on a different computer.