Most likely the cable but you said you tested it. I recommend a full factory reset of the router if you don’t have too much custom configured. Also check the Ethernet going into wan? Do other devices have any issues. Wi-Fi? Another laptop/desktop to test? Maybe try a usb—>ethernet to rule out the port on the laptop? Change lan ports on router? Idk, could be a lot of things. Hopefully some of those help
Most likely the cable but you said you tested it. I recommend a full factory reset of the router if you don’t have too much custom configured. Also check the Ethernet going into wan? Do other devices have any issues. Wi-Fi? Another laptop/desktop to test? Maybe try a usb—>ethernet to rule out the port on the laptop? Change lan ports on router? Idk, could be a lot of things. Hopefully some of those help