To fix:
1. Have the user shut down the computer then unplug the router (or network cable if not on WiFi) and leave it unplugged for now.
2. With the router still off have the user start the computer back up and log in as they normally would,
3. Once logged in the user can now start the router (or plug the network cable) back up.
4. Be sure to check office and Windows updates once the user is back connected to the internet.