Plutonium

I have wasted so much time to get plutonium and when I finally do get it it never wants to work. I've tried to play custom games in zombies with my friend for days now with UpnP turned on and my ip being sent and it never works. Any ideas? Or at least a tutorial? idk.

I'm seeing these posts about having upnp, what is it? and how do I turn it on?

The game won't start up because apparently i'm missing something. The thing pops up during initialization.