Hi. Sorry to ask again, but you hold the left button while switching on power?
Even if not connected with a cable, it should read "usb not connected" on the lcd.
(And it doesn't load the OS in this mode).
Then when connecting the usb cable, it should read "usb connected".
If you get as far as the "not conn" msg, try different cable, diff usb port, diff pc.
Best, Deve.