once your wifi on an iphone greys out its pretty much gone......you can look on youtube, there are some videos on there of how to possible get your wifi back on. Like theres the freezer method, resetting your phone to factory...i know I had an iphone 4, my wifi greyed out, I tried everything and couldnt get it to work, but thats because I accidently left it out in the rain.....worst mistake I ever made buying an iphone, I switched back to android....good luck..hope you find a solution....:)