It happened to me too 1 week ago when just stopped out of the blue.The board turns on ok, green led blinking but no pc can detect it anymore . I'd like to mention that my micro usb connector is firm and tight, soldered onto the board as I ironed & hot glued it first time after I unpacked 6 months ago. Any suggestions are welcomed, thx!
You could try to "CANBUS" it to a working board