Hi,
Couple of things.
1. Have a look with a magnifying glass into the ethernet port and make sure that none of the connector strips have moved out of position, i.e. that they are all straight and parallel.
2. As it might be the controller chip that is faulty, it may be easier to use a USB WiFi adapter so that you can connect your Xbox to your wireless router for internet access, than to try and replace the chip.
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