The network setting may be incorrect.
Check that the power is turned on.
supplementary explanationFor details, refer to Turning On/Off the Power.
Check the LAN cable.
supplementary explanationFor details, refer to Interfaces used for connection.
Check the IP address.
supplementary explanationFor details, refer to Main network settings.
Check the connection on the command prompt.
supplementary explanationExample: C:\>ping 192.168.0.1