WDI4500 units with some firmware versions default to SNAPI mode instead of HID (keyboard) mode, meaning they won't send barcode data. To work around this, after setting the scanner to factory defaults (page 2-4 of User's Manual), scan the HID Keyboard Emulation barcode (page 3-4) to change it back from SNAPI to HID. If the scanner does not emit a beam after this barcode has been scanned, unplug then replug USB cable to get it to work again.