It may be a hardware issue if that's the case. If your device is still under warranty, you can have it replaced. If your 1-year manufacturer's warranty is over, you can still bring it to a Genius Bar to have the diagnose to see if the issue is indeed a hardware issue, then you can explore options from there. Also check your network setup, and possibly resetting your router
I have a 4S and am having issues with my wifi connectivity as well. I ran with wifi on all the time so that I was on either home or work network, and not placing a drain on the Verizon Network (I have unlimited Data [grandfathered in] so the motivating factor was purely speed.) I searched and found this thread:
It sounds like the hardware has failed. That being said, my problem is that going into the Settings and attempting to turn on the wifi will result in one of two scenarios: 1. The wifi slider will not be clickable. 2. The slider will be, I will slide it to the "on" position, the phone will start to ask very slowly, possibly freeze (requiring a Power/Home button reset), and then when I have forgotten all about the issue and go to look at the phone, it will have powered itself off.
Swiping up from the home screens, and selecting the wifi icon will result in an illuminated icon, and not much else...
I had an update (7.0.4) that was awaiting a wifi connection that I finally did via iTunes. No change in performance or connectivity.
What say you iPhone mentors? Is the wifi chip cooked and I am in need of a new phone to get wifi?