I've done a clean install of OS X El Capitan recently, and everything worked fine.
But as I came home, I couldn't connect to Wi-Fi. It states that it has a self-assigned IP address and will not connect to the Internet.
I've been on many forums, and found no solution. Wi-Fi normally worked before the clean install and it still works on my side system, Kali Linux, which I'm writing from right now.
I've tried to get OS X forget the Wi-Fi and then input the password again, but nothing changed. I've tried to enter a valid IP that I know it's working (I got to it through an app which remembered my computer on the Wi-Fi back when it worked), but still no Internet for me.
The Wi-Fi has WEP encryption and I'm not able to access the router to change any settings, because the owner (which is not me) refuses to let me do some adjustments.