It first enters the system to see if the computer's network settings are correct, and the internet connection methods are different in different environments (generally there are computer dialling, router dialling or fixed IP/DNS internet connection through switches). under the condition of confirming the computer's network settings are correct, it is generally possible if the network is not connected:1. The built-in network cable is not connected. The built-in network cable can be tested by a network cable on-off instrument. If it is not connected, it can be directly replaced.
2: or if the mesh port on the USB module is not properly welded or damaged, judge whether there is any problem with the mesh port on the USB board, and first observe whether there is leakage welding, virtual welding or false welding. if there is any soldering iron, add welding with the soldering iron; if not, the mesh port may be damaged;
3: The main board's network port itself is damaged (it can be judged simply first. The straight-through network cable can check whether the two LED lights at the network port end are always on or flashing. If the LED does not respond, the network port can be judged to be damaged).