I am disheartened to see many other folks posting the same complaints about the same issue I seem to be having. The other day my wifi and Bluetooth features of my iPhone 4s suddenly stopped working. The wifi is greyed out and the bluetooth just keeps spinning and won't turn on or off. I use both features regularly and can't afford to be without them even for a short while. I have reset the phone from scratch, run it down dead, cooled it in the refrig to no avail. What to do?
This is a known problem with the iPhone 4s and the only solution is a new phone. I was lucky and it happened while mine was under warranty. I hope yours is, too!
Of course this begs the question, why is Apple selling phones with this problem?
Unfortunately most iPhones that experience the greyed out WiFi button require replacement. You can try to do a factory reset via iTunes, but if that doesn't work you will need a new device.