What is the reason?
The fault may be, for example, in the router, which is used by the user or the operating system. The most common causes, in which Wi-Fi is not displayed or does not see the laptop, can be connected with the fact that Wi-Fi router is hung or is not configured, there may be different problems with the device that connects to Wi-Fi Internet access is blocked by a firewall or antivirus, and DHCP on the router does not give IP address.
Troubleshooting
To determine the cause and subsequent fix requires to check the router. This should restart the router and see whether there was displayed a network in the list. If this still did not happen, then you must unplug the network cable from the router and move it to the appropriate connector on the laptop.
This will allow you to check whether it comes from the Internet provider or not. If the Internet does not arrive, then it directly to the service provider, otherwise, you will need to configure the router. For configuration, you must navigate to the address 192.168.1.1 or 192.168.0.1 depending on the router model.
If in the settings all in order, then you need to update or install the driver for your network adapter. They can easily be found online, but you need to know the model. To do this, open "control Panel" and select "device Manager". In the list you want to find the "Network adapters". Here is a list of all network devices on the computer, and in order to find Wi-Fi, you should select, where there is the phrase "Wireless device...". After searching and installing all drivers, a Wi-Fi network should be displayed.
If none of these methods did not resolve the urgent problem, then most likely the problem lies directly in the device that is trying to locate and connect to a wireless network. To check this, you can buy an inexpensive USB adapter for Wi-Fi or borrow it from a friend and install it on the laptop. If the problem really was to it, then it will detect wireless networks.