Possibility 1 is that you don't have a WiFi card/dongle attached to your PC. Not all PCs have WiFi built in, so buying a WiFi USB dongle should solve things. Possibility 2 is that something's gone screwy with your WiFi drivers, possibly due to a large update to Windows (like the Creators Update released in the last week). If so, download the latest WiFi drivers from your PC manufacturer's web site and install. If this doesn't work, you may have Possibility 3, your hardware is broken. Image your boot drive to your external backup drive (Windows has an imaging system built in for this), then wipe your boot drive and clean install Windows and your basic drivers. If that works then you know it isn't your hardware that's broken down. You then have the choice of restoring your image and experimenting/fiddling to find the fault, or just taking this as a sign it's time for a clean install.