If you plug the board into your PC while firmly holding down the pushbutton--and the blue LED does not turn off--then it is either in bootloader mode or the board is damaged. If it is bootloader mode, you'll get device enumeration via USB. If it doesn't enumerate (on any PC) in this condition, then something somewhere has is damaged Chris
I finally just found this. Sadly then, it seems my new boards are broken. Not seeing anything under the Other Devices or Ports sections of the device manager while clearly in bootloader mode.
This was driving me nuts, I was so sure I was following everything to the letter. Glad I can finally put it to rest.