Hi, I've got a problem with Wifi connection. Everything was working fine, when suddenly I am not being able to connect to the Internet using Wifi. I have tried googling around, but what I found is the incompatibility between router settings and S4. In my case, the router works well until suddenly it refuses me my Internet. No settings have been changed at all, no updates whatsoever.

Can somebody help me?

Galaxy S4 I9505
Android 4.3