Check any cables and reboot any routers, modems, or other network devices you may be using.

If it is already listed as a program allowed to access the network, try removing it from the list and adding it again.

Check your proxy settings or contact your network administrator to make sure the proxy server is working. If you don't believe you should be using a proxy server: Go to the Chrome menu > Settings >Show advanced settings… > Change proxy settings… > LAN Settings and deselect "Use a proxy server for your LAN".