You can do this with the little physical button situated at the base or in your router settings.
Every router has a dedicated Wi-Fi switch, so ensure sure Wi-Fi is turned on. Turn it off and stand by some time before turning it back on. On the other hand, if none of the available devices can connect, check the steps I’ve given below:
If you can connect and Internet access is completely functional, proceed with the other step. The obvious way is to try to connect to the network and check using another device, like a smartphone, or another PC. To start with the router is the one causing Wi-Fi issues.