Other devices, and PCs and it works perfectly. I replaced the motherboard...nada. Reformatted...nada. The mac address didn't banned on the router or modem and there's no ip address conflict because it's not even obtaining an IP. This is both on DHCP and a static IP. It's a Windows 10PC and a Netgear router with the latest firmware.
Very strange. Of course you have tried the obvious like a different cable, I'm sure. You may want to try a USB to ethernet dongle on that machine. These are available from Amazon and others for $20 or so. When you plug is, do the lights on the router indicate that a connection has been made to that port? Try the connection with a short cable right next to the router. I assume the ethernet connector in the laptop is part of the motherboard so it was replaced with the motherboard was?
It's a PC. I have tried a different cable, but since it works on my other PC and my laptop, I don't think it's that or the wall port. Also I've uninstalled the ethernet adapter through the device manager and installed drivers. I haven't tried a dongle, but since I've replaced the motherboard and thus the ethernet port, it's not the port itself. It also worked when it was connected directly to the router. But not with the port. But nothing is wrong with the wall port.