WiFi access points are devices that allow one to connect to network/internet sources through their own WiFi enabled device. The more available access points nearby, the more accurately we can locate you. Your device does not necessarily need to be connected to any of these networks, but simply must be able to 'see' them.
If your device cannot see enough WiFi APs, it will be difficult to locate you. This may occur in rural areas or even in very tall buildings. Try moving to an area with more APs nearby, or using a WiFi extender in order to detect more APs that may be a greater distance away.