After upgrading to iOS 9.1 wifi cannot turn on ! Grey out wifi on iPhone 6 plus

Hi. Check this link: If Wi-Fi is grayed out or dim on your iPhone, iPad, or iPod touch - Apple Support

If it does not help try to reset/restore your device to factory settings.

To reset your device:

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

If this does not help, restore your device to factory settings. Note that this will erase the data from your device.

Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.

Doesn't work.

Even after factory reset, to a blank "new" iPad with updated iOs 9.1 installed via iTunes, the grey Wifi switch remains.

Frustrating...

Take you device to the Apple Store.

The only solution to the greyed out Wi-Fi button after an IOS upgrade is the "hair dryer" solution. Believe it or not, it works and there are plenty of YouTubes showing how to do it. It apparently resets the wi-fi chip with a thermal overload. The first time worked for about 6 months. Just had to do it again tonight and luckily it worked again. Absolutely sickening that Apple would stoop this low to sell new phones. I'll never buy another Apple product. IOS upgrades kill this indispensable function on older phones (ours is a 4S). If you call Apple support, they'll tell you its completely a coincidence that it happened at the same time as your upgrade, and SURPRISE!!!!...you should buy a new iphone. But hey...no problem you might think...I'll just go back to the older IOS. Uh, no. They stopped supporting it and you CAN'T go back. Folks, that's freaking evil. I'm furious. Hundreds of billions of dollars and they pull this kind of crap. Never again. Our next phones will be Android. Period. I hope their arrogance someday catches up to them.