Wi-Fi search Shows nothing or It wont connect to a network.
Turn Off your WiFi and turn it ON again. Settings > Wi-Fi
Restart your iPhone/iOS device.
Restart your Wi-Fi modem/router.
Reset network settings : Settings > General > Reset > Reset Network Settings.
Try deleting the the network from your iPhone's wifi settings by clicking on the blue arrow icon on the right of the network name then touch forget this network. restart you phone and create a new connection.
Upgrade firmware of the Wireless router to a latest version released by the vendor. checkout manufacturer's documentation for more details.
Unable to turn on Wi-Fi
Some users might find this difficulty such that there is no Wi-Fi address found in Settings > General > About. This makes the setting NA/00:00:00:00:00. So that Wi-Fi or Bluetooth settings grayed out or dim.
Airplane mode simply disables all network connections including W-Fi and bluetooth on you phone. Make sure that Airplane Mode is off.
Restart the device and try again. This may be a bug. Check for latest updates of your iOS version.
Reset Network Settings.