How to create a multiplayer?

I work with the big project. But when packing I had a lot of problems. One of them - a multiplayer.
I created the new project to show a problem.
I created a simple multiplayer:

And it work:

But after packaging project - the multiplayer doesn’t work:

I add :
[OnlineSubsystem]
DefaultPlatformService=Null

in DefaultEngine. But it don’t help.

The project Launcher works well:

79545-10.jpg

But the multiplayer doesn’t work too. In the console at attempt to create session or find session - writes these errors:

Please, help me. What I need to do for solve a problem?

Hello,

I highly recommend viewing our new Blueprint Multiplayer tutorial series: https://www.youtube.com/playlist?list=PLZlv_N0_O1gYqSlbGQVKsRg6fpxWndZqZ

This will give you all the information needed to set up your multiplayer game.

Have a great day