Hello KARKAT_VANTAS34
Looks like either the Ethernet card is faulty, or its correct driver is missing. Can you please confirm if it is a desktop computer or a laptop?
Assuming that it is a laptop and the Ethernet card driver is missing, you can try the following:
To confirm if the NIC driver is missing:
> Right-click the
Start button.
> Click
Computer Management from the context menu.
> From the left pane of the
Computer Management snap-in, click to select
Device Manager.
> From the right pane, expand the
Network adapters tree.
> Check if your Ethernet card is present with an exclamation mark within a yellow triangle. If it is present, Windows 10 can detect the card and needs its driver. If nothing is displayed under the
Network adapters tree, you can right-click it and click
Scan for hardware changes to see if Windows can detect the card this time.
> In case the Ethernet card is still not visible, it may be faulty and since you have built your PC recently, you can claim its warranty.
To detect the correct driver in case the Ethernet card is present:
> Press
Windows +
R keys.
> Type
MSINFO32 in the
Run command box and press
Enter.
> From the left pane of the
System Information box, expand the
Components tree.
> Click to select
Problem Devices.
> From the right pane, note down the displayed device ID and search for its driver online.
> Download and install the driver to bring your Ethernet card to life.
Hope this helps.