StViewer supports only USB3 Vision cameras and cannot be used with other USB cameras such as USB2.0.
Even with USB3 Vision cameras, the camera may not be recognized if the USB 3.0 host controller driver is not installed on the PC or if the camera is not receiving sufficient power.
Check in Device Manager and on the manufacturer’s website that the USB 3.0 host controller driver is properly installed and updated to the latest version.

Some USB3 Vision cameras, external power input through the 6-pin connector is recommended.