At this point I would have to think about RMA'ing the MB. If the driver cannot find the adapter, it may be defective. But...
Does your BIOS have a Lan test option in it? Older boards used to have that, but I think yours may not.
Go to page 92 of your MB manual and try to set up your internet connection used to flash the BIOS from inside the UEFI. See if that works. If you get the internet connection, it would mean the LAN adapter is functioning.