Sometimes your WiFi can get disconnected without reason. I had it repeatedly after one day of continuous streaming during the world championship tournaments. Windows 8.1 and 10 both had it, so it was probably more the fault of the WiFi stick driver. In Windows no action of any sort helped. It showed the disconnected symbol and if clicking on it there were no WiFi networks visible even that the phone just right beside still had a perfect connection. Also the built-in repair function of Windows didn't find the reason. Logout of the current user didn't fix it either. The first time I feared that the WiFi stick was gone, maybe too hot or so. But after a full restart of the PC it worked again as if nothing had happened before.
After some more experiments I found that disconnecting and reconnecting the WiFi Network Adapter cured the problem. So I embedded a new function into Mighty Desktop, in the Devices tab (of the tab 'Toolbox'):
The button is called Reconnect Network Adapter: It can disconnect one of the network adapters in the Network Control Panel for any period of time and reactivate it. With "Restart Devices" checked it cured the problem in the shortest possible time.
Note: If "Restart Device" is switched on the WiFi adapter can forget the stored network password. So be prepared to have that near you in case the driver asks for it.