Here are some suggestions that might help ;
- Double-check if your webcam is plugged in, turned on, active and working. You can click Tools >> Options >> General >> Video Settings to check if your webcam is detected by Skype. If possible, also test your cam using other program/software.
- Update your latest version of Skype. Visit the "Get Skype" (Downloads) section of Skype.com to check the most recent version of Skype available.
- Update your webcam driver or software. You can visit the corresponding manufacturer's site to see if there is a newer version of driver/software for your webcam model.
- "completely" uninstall Skype first then re-install. Please note that the process of complete uninstall differs from the usual uninstall as it will delete all traces of Skype in your computer. Thus allowing users to install a fresh/clean copy of Skype. In most cases, it is also advisable to use the most recent version of the Skype software.