StViewer cannot use USB2.0 or USB3.0 camera. USB3 Vision camera can use with StViewer.
USB3 Vision camera may not recognize, if driver for USB3.0 host controller on PC does not install, or USB bus power does not enough for USB3 Vision camera.
Please check latest driver for USB3.0 host controller on PC.

Some USB3 Vision cameras are recommending to use external power supply through 6 pin connector.