Ross-Tech USB Interface Not Found: VCDS-Lite will show this if you try to select the "USB" button in options. The KKL 409.1 cable is a serial-to-USB bridge, so you must always select the COM port number, not the USB button.

You will need the drivers and the VCDS software. Here is a breakdown of the most reliable sources:

Look for an item under Other Devices or Ports (COM & LPT) with a yellow warning triangle. It usually says USB2.0-Serial or USB Serial Port. Right-click that item and select Update driver.

If you see "Port Status: Not Found" or "Interface: Not Found", go back to Step 4 and verify your COM port number and driver installation.

Also ensure the port settings match these values (from the same Port Settings tab):