Fresh created Third Person Template. Number of players set to 2.
This is the arguments I used
D:\UE_4.17\Engine\Binaries\Win64\UE4Editor.exe C:\Users\David\Documents\CPP_Project\CPP_Multiplayer\CPP_Multiplayer.uproject /Game/ThirdPersonCPP/Maps/ThirdPersonExampleMap ?listen -server -log
D:\UE_4.17\Engine\Binaries\Win64\UE4Editor.exe C:\Users\David\Documents\CPP_Project\CPP_Multiplayer\CPP_Multiplayer.uproject /Game/ThirdPersonCPP/Maps/ThirdPersonExampleMap 24.144.32.53:7777 -game
I get 0 warnings or errors. It just doesn’t connect the two players to the same room, ever. PIE works fine.