A number of iPhone 4S owners these days posted their Wifi problems to Apple discussion forums or Apple’s support forums, mentioning that they encountered the grayed out Wi-Fi button or "unable to connect" message many times after they upgraded the iPhone 4S to iOS7. They complained the grey-out or dim Wi-Fi button issues only happen after the iOS 7 update. If this occurs, the Wifi option in the iPhone 4S is unavailable, so when 4S owners tap the Settings > Wi-Fi, trying to turn on the Wi-Fi, the iPhone 4S fails to respond. According to some reports, the annoying Wi-Fi problem for the iPhone 4S may be caused by the iOS 7. There are some useful solutions to fix the iPhone 4S Wi-Fi connection problem below.
Turn off the airplane mode by tapping Settings > Airplane Mode, then do the network resetting by tapping Setting > General > Reset > Reset Network Settings, and finally restart the iPhone 4S.
Note: If you reset the network setting, all recorded data will be removed, such as the Bluetooth pairing records, Wi-Fi passwords, VPN as well as the APN settings.
You also can try this Wifi solution for iPhone 4S: Setting > General > Reset > Reset All Settings.
Note: This troubleshooting may fix the Wifi problem, but it will remove all of your preferences.
If you have tried the above solutions, but still face the iPhone 4S Wifi issue, you can check if your 4S is upgraded to the newest available software. You can restore the iPhone 4S after checking the software updates in Apple iTunes.
Note: Restoring the iPhone 4S as a new phone is a slow process and it will reset your 4S to the factory setting. But you need to reload all your contacts or media information to the iPhone 4S after connecting your device to the computer.
Some forums threads suggest another solution to fix the "gray out" iPhone 4S Wifi issue: placing the iPhone 4S in a refrigerator or freezer for several minutes, for they considered the 4S WiFi issue after iOS 7 update is caused by the heating issues.
Note: The lower temperature in the refrigerator or freezer may cool down the heating WiFi radio chip and will temporarily solve the WiFi problem for iPhone 4S, but the warm and cool temperature shift between the refrigerator or freezer and the room may cause the potential damage to your iPhone 4S.
If the Wi-Fi switch is greyed out or dim on the iPhone 4S after you do the iOS 7 update, it may be related to the software problem rather than hardware problem. Therefore, in order to get your 4S WiFi working again, you can downgrade the previous iOS to resolve the problem for your handset.
If the iPhone 4S Wifi connectivity trouble is still unable to be worked out, you can contact Apple Customer Service for the service options or visit the Apple Store for the direct solution.
If you have iPhone 5S or iPhone 5, you can check How to Fix the iPhone 5S/5 Wifi Problems. Or if you have any other Wi-Fi issues on your smartphone, let us know in the comments below.