I understand your frustration with the network connection issue on your Arduino MKR WiFi and Ethernet Shield. It seems that when you connect it to a different USB cable or a second PC, it fails to obtain the static IP address and the network connection stops working. One possible cause could be the power supply or the quality of the USB cables used. It's crucial to ensure a stable power supply to the Arduino to avoid such issues. I recommend checking the power supply and the quality of the USB cables to resolve the problem and maintain a consistent network connection.