Sometimes you will plug in your device to get the evidence and your computer will no longer recognise the device.
This is a common issue that happens will all USB ports and devices from time to time.
To resolve this you must follow some steps. Below is a great article to assist you.
You may also have a damaged USB cable or plug. Blow out any dust and try again, if that fails try a different cable or try that cable on a different device. Many OzSpy products use standard plugs and leads so you should be able to find another that fits.
Be careful not to apply force to USB connectors or wriggle them in place as USB is a sensitive plug type.