You may need to restart your PC. To do so, press Windows key + R on your keyboard and type msconfig into the dialog box then hit Enter or click ok. Then find Startup Section in the window that appears. Find a setting called Network Connections. It should be at least 3-4 lines long with a list of network adapters (if you have more than one). Double click on any entry and it will open up its properties page which has troubleshooting options such as Restart Network Service, Disable this adapter etc...