The Wireless Router or Access Point is Turned Off or is Not Working Properly
If Windows does not detect a network that you think is in range of your computer, it could be because the wireless router or access point is turned off or is not working properly.
There are two things to try:
Warning: Resetting the router or access point will temporarily disconnect everyone from the network. If you do not manage the access point or network, contact the network administrator.
Note: This information provided by Microsoft.