When connected to the internet with your internet service provider, it may happened that Windows display the following message: "A network cable is unplugged"
This happened whenever the network connection has failed.
It is however recommended not to use a connection USB port. A connection with the Ethernet network with a cable RJ45 is more efficient.
You should also avoid connection of more than two meters between your modem and your telephone plug. However the network cable between your computer and modem can be around 10 meters.
Moreover if your modem does not possess a connection with RJ45 cable, contact your internet service provider