1. Check whether the network port is disabled. (For Windows, you can check the Device Manager or "Control Panel\Network and Internet\Network Connections"; for Linux systems, you can use the IP -a command to check whether the status of the network card is up.)

2. Check whether the connection of the network cable is defective (replace with a new network cable for verification test);

3. Whether the equipment at the other end is defective (including system, network port, etc.);

4. Check whether the connection rates at both ends match (generally the default is adaptive);

5. Replace the network card and check whether the individual network card is defective.