Server Hosting wont show up after a Video guide.

So i watched this Video: Unreal Engine 4 Steam Multiplayer Tutorial (Blueprint): Hosting and Joining Games - YouTube and at 38:00 its about Server Hosting and Server Browser stuff but the Hosted Server wont show up. And i watched it 3 times again and checked if i did everything right and i cant find the problem. Did anyone run into the same problem?