Local multiplayer JoinSession not working. TravelFailure: LoadMapFailure

I am trying to connect to my hosted multiplayer game in my LAN. Actually, for two days now. What I get is the following log:

[2017.02.09-14.22.44:881][432]LogLoad: Took 0.023728 seconds to LoadMap(/Game/Maps/UEDPIE_0_MainMenu)
[2017.02.09-14.22.44:881][432]LogNet:Warning: Travel Failure: [LoadMapFailure]: Failed to load package '/Game/Maps/UEDPIE_0_LobbyScene'
[2017.02.09-14.22.44:881][432]LogNet:Warning: TravelFailure: LoadMapFailure, Reason for Failure: 'Failed to load package '/Game/Maps/UEDPIE_0_LobbyScene''. Shutting down PIE.
[2017.02.09-14.22.44:881][432]PIE:Warning: Warning TravelFailure: LoadMapFailure, Reason for Failure: 'Failed to load package '/Game/Maps/UEDPIE_0_LobbyScene''. Shutting down PIE.
[2017.02.09-14.22.44:882][432]LogBlueprintUserMessages: Early EndPlayMap Detection: Level '/Game/Maps/MainMenu.MainMenu:PersistentLevel' has LevelScriptBlueprint '/Game/Maps/MainMenu.MainMenu:PersistentLevel.MainMenu' with GeneratedClass '/Game/Maps/MainMenu.MainMenu_C' with ClassGeneratedBy '/Game/Maps/MainMenu.MainMenu:PersistentLevel.MainMenu'
[2017.02.09-14.22.44:923][432]LogOnline:Display: NULL: FOnlineSubsystemNull::Shutdown()
[2017.02.09-14.22.44:932][432]LogPlayLevel:Display: Shutting down PIE online subsystems

Now, the LobbyScene is present and works great when I host the game with that computer. The other computer that hosts the game actually IS on that LobbyScene, and it has the exact same installation folder as the client computer, freshly copied over.

I also tried the same with a packaged game, a standalone game and every other possible way I could think of. It just does not work for me.

I also tried the same using Steam, no go. With a second Steam account on another computer of course.

And as you can see in the pictures I actually use a plugin now in the hope that AdvancedSessions solves my problems. But it also did not help. Before that I was using the standard to create sessions, same results.

I am on the same network, only a switch between the computers. I completely disabled all firewalls on the computers by now.

Maybe the error is in here? DefaultEngine.ini

[/Script/Engine.GameEngine]
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="OnlineSubsystemSteam.SteamNetDriver",DriverClassNameFallback="OnlineSubsystemUtils.IpNetDriver")

[OnlineSubsystem]
DefaultPlatformService=Steam
bHasVoiceEnabled=true

[OnlineSubsystemSteam]
bEnabled=true
SteamDevAppId=480

[Voice]
bEnabled=true

[Core.Log]
LogOnline=all
LogOnlineGame=all

[/Script/OnlineSubsystemSteam.SteamNetDriver]
NetConnectionClassName="OnlineSubsystemSteam.SteamNetConnection"

or maybe in here? Build.cs

public class Helden : ModuleRules
{
	public Helden(TargetInfo Target)
	{
		PublicDependencyModuleNames.AddRange(new string[] { "Core",
                                                            "CoreUObject",
                                                            "Engine",
                                                            "InputCore",
                                                            "Sockets",
                                                            "Networking",
                                                            "VRExpansionPlugin",
                                                            "AdvancedSessions",
                                                            "OnlineSubsystem",
                                                            "OnlineSubsystemUtils" });

		PrivateDependencyModuleNames.AddRange(new string[] {  });

        DynamicallyLoadedModuleNames.Add("OnlineSubsystemSteam");

        UEBuildConfiguration.bForceEnableExceptions = true;
    }
}

So yeah. Please ask further questions. I have no idea why it is happening, logging does not show anything, I can’t really put breakpoints into that code either.

http://hqcloud.de/temp/mp1.png

http://hqcloud.de/temp/mp2.png

http://hqcloud.de/temp/mp3.png

http://hqcloud.de/temp/mp4.png

If you want to load a map you shouldn’t put “open level” block. You should put a console command saying
“servertravel /Game/Maps/ExampleMap01”. Make sure it has a space between servertravel and the slash.