Wi-fi button is greyed out, can't turn it on or off?

My 4s did the same thing, after being updated for two days. I spoke with Apple and Verizon, and they (Verizon) said the update "screwed" up my phone. Verizon offered to send me a replacement for the low price of $199.99. I tried everything, restoring from previous backup, restore as new phone, airplane mode on and of several times, reset network settings. It is my best guess that this is purely a software issue. Looks like the only quick solution is buy a new phone.

My 4s Wi fi button was greyed out and inoperative too. This afternoon a combination of actions happened that has allowed me to get back on my home network wi fi connection and I posted it at this link

https://discussions.apple.com/thread/4312636?answerId=19698150022#19698150022&ac_cid=tw123456#19698150

hope that helps you.