I also had this problem today, but in my case I think it had to do with 3g unrestrictor. When I got back from work, I noticed my iP4 wasn't picking up any wifi signal from my network or any ssids around me. I haven't used the app for a long time, so it lead me to believe that was the cause. I was able to fix the wifi by doing a reset, holding both the power and home button.
Good luck finding the cause.