If the system doesn't detect a connected USB drive:
USB drive not detected by system
Remove and reseat the USB key. The USB key may not be connected properly to its input jack on the control console. Disconnect and firmly reseat the connector
Try the USB port on the back of the console. There is another USB port on the rear of the control console
Try a different USB key. The USB key may be defective
Perform a control console reset:
Turn off the control console, then press and hold the POWER button for five seconds
When the red LED turns off, release the Power button and retest the system