Iphone 4s wifi button is greyed out and won't turn on?

We've tried resetting the network settings, using the hairdryer turning it off for 5 minutes or whatever. But nothing works. Any help?

Verify that airplane mode is off by tapping Settings > Airplane Mode.

Reset the network settings by tapping Settings > General > Reset > Reset Network Settings.
Note: This will reset all network settings, including Bluetooth pairing records, Wi-Fi passwords, VPN, and APN settings

Ensure that your device is using the latest software. To do so, connect your device to your computer and check for updates in iTunes.