Yawcam -> Detect webcam
The function "detect webcam" scans your computer for video capture devices and shows a list of the found devices. Use this option if you have connected a video device when Yawcam already is running.
If the only option in the list is "none", Yawcam couldn't find any devices.
You can access this function by clicking "Settings -> Detect webcam..." in the text menu in the main window: