This normally happens when your free trial and/or license have expired for some time. 

• If you think this machine should be licensed, check to see if your Ethernet connection in the Network Connections control panel is disabled.
  • To re-enable, go to Start -> Control Panel -> Network Connections, right click on your disabled connection, and select "Enable".
• If you want to work without a network connection for security reasons, you can unplug the network cable but still leave the network adapter enabled.