Would suggest a possible issue with the software/hardware in the car, if they have all the right files? At least they should refund if they cannot produce a working version.
Have used them myself and the products have worked they have many customers using their products, so which is more likely - they have sent a faulty usb or there is an issue with your software/hardware?
Just checking you have asked for the right version - checked this on the Nav system? Use the Lexus Map update page to check.