This article is aimed at helping iPhone 6 users who are having trouble in making changes to their phone's Wi-Fi settings as it appears to be grayed out or dim. While this is a rare case, some iPhones have Wi-Fi settings that cannot be changed, as the device will not respond when you attempt to turn the Wi-Fi on.
For iOS 7.1 versions, the problem is associated with an error prompt saying, "Wi-Fi not available," which displays in the Control Center.
If you too are having the same issue with your iPhone 6 or iPhone 6 Plus, then here's what you need to do to get it fixed. Be sure to test your device after performing of the following methods to see whether the problem is already fixed. Otherwise, proceed to the next step.
1. Restart your iPhone.
To do so, press and hold the Sleep/Wake button until the red slider appears. Drag the slider to completely turn your iPhone off. After the device powers off, press and hold the Sleep/Wake button again until the Apple logo appears.
2. Verify the Airplane mode is turned off.
Tap on Settings, then select Airplane Mode. It must be off or disabled.
3. Reset network settings.
Tap on Settings, select General, tap Reset, then select Reset Network Settings. When you do this, all network settings including Bluetooth pairing records, VPN, APN settings, and Wi-Fi passwords will also reset. So be sure to back them up first.
4. Update iPhone to the latest software.
Please note that the first released version of iOS 8 contains some bugs, which are immediately addressed by Apple with the iOS 8.2. So better check your device software and see if you need to go for a firmware update this time. You may also check for updates in iTunes if you want.
If you still cannot enable Wi-Fi on your iPhone 6, then please contact Apple support for further assistance and service recommendations/options.