This is not a problem regarding IP if it detects the cable is unplugged. If the physical connection was fine but there was an IP problem, it would be listed as having Limited or No Connectivity.
Make sure the cable is securely snug in the ethernet port on both ends, and that the connectors on the cable and the cable-length itself is not damaged. If you are trying to connect to a router or modem, make sure you are using a straight-through cable, not a cross-over.
Do you have another cable to test with? If you have a spare cable, try plugging that one in instead using the same ports and see if it still detects the cable unplugged. Also, try plugging the cable into a different port on your router/switch (if you have one), just to check and make sure the port itself on the device isn't borked.
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