I had already read that page.
All the other LEDs are on and I remove the SD with the same result.
While my crystal ball is usually pretty good, it missed that. I'm sorry.
If you have 3.3v LED when powered by (just) USB and the the board is not detected by the computer, odds are the processor is damaged and there is nothing to loose by trying the erase jumper procedure at the bottom as the board is "completely unresponsive" and there is no reason to suspect the USB cable is the problem as it previsouly worked.
If it doesn't give you a usb serial port to recover with BOSSA maybe upload some clear high resolution pictures to see if it helps determine the extent of the damage; but the board will need surface mount rework to function one way or the other.