4s says no wifi

This happened once on my old iPhone 4. It's a hardware issue. Take it back to Apple (or where you got it) and they should replaced it for you.

Try this !

http://support.apple.com/kb/TS1559

It worked for me, in the short reset net work settings !

To do this, tap Settings > General > Reset > Reset Network Settings

you will need your router pass key again !

It worked. Thanks!

This worked for me too. My phone randomly turned off so I had to hard reset (Power + Home Button for 10 seconds). When the phone turned back on, it had the Wifi option greyed out in settings. Resetting the network settings seems to have fixed that.

IT has happened to mine about 3 - 4 times now, just hop there is a fix in next update !😮

All i can think off is try to restore it..... Hope that helps !

Had same problem for first time today. Switch off -> no wifi.

I have found since my last reply, if you get this lock up, when you get it going again you get the greyed out "no Wi-Fi" thing, if you reset phone again, it all returns to normal !

This WORKED! Thanks. Rediculous to take it into Apple when a simple reset fixes the issue for me. Thanks.

Not correct! Reseting my network worked, so it's not a hardware issue.

I'm referring to the no wi-fi issue, not your particular case. I'd hate for people to think the correct course of action is to try and get a new phone with the idea that the issue is hardware related. Since a few of us with this issue were able to fix it with a network reset I just want to inform others finding this thread that the hardware/replacement solution is not the correct answer in all cases.

This worked for me! Thank you so much! The closest Apple store to me is 3 hours away!

You can also solve this by just restarting your device wich worked for me.

i have the same problem, no wifi after i did software upgrade to 5.1.. did reset network, reset all setting, erase all, restore, hard reset, none of them worked. i think i'm gonna get a replacement today