iPhone 5, iOS 8.1.3, wifi greyed out

iPhone 5

iOS 8.1.3

Wifi button is greyed out, unable to turn it on to connect to wireless.

I have tried turning airplane mode on and off, turning cellular data off, restarting phone, resetting phone, etc. I finally restored the phone to its factory settings but it did not fix the problem.

My battery did die completely yesterday and when I plugged it in I noticed the wifi switch was no longer greyed out. It went back to being greyed out before I was able to enter my wireless password and connect.

Thank you!