Is Airplane Mode on? If so, turn it off.
If it is off, it could be an issue with your WiFi Adapter. Click on the Notifications Icon in the bottom right next to the time and choose All Settings. Then Select Network and Internet. Click on WiFi and make sure your WiFi adapter is listed. Someone above mentioned using FN keys to make sure your WiFi adapter is turned on. Not all laptops do that, but it is a good place to check as well. Some laptops also have a physical switch or button to turn the WiFi Adapter on and off. Check for one and make sure it is on.
It is totally possible that the internal WiFi adapter has gone bad or a Windows Update/Driver Update may have corrupted it, which is why you don't see the WiFi icon in the bottom right like you normally would. If it is a case of a bad Driver Update, you should be able to roll it back. Go to the Device Manager (click Cortana in the bottom left, next to the start button) and type in Device Manager. The look for Network Adapters. Your WiFi adapter should be listed there. If there is a problem with it, there will be a little Yield Symbol on the icon. If you don't see a WiFi Adapter there, it most likely has been turned off. You can also check for Unknown Devices. If you have one, it could be your WiFi adapter, but something may be wrong with it, which is would keep Windows from recognizing it and showing it in Network Adapters where it belongs.
A cheap and easy fix if all else fails, just buy a USB WiFi adapter. For as little as $10 on Amazon, you'll be back in business. Staples or Best Buy will have them as well, but probably will be more expensive.
-Michael