Level(s) is missing after (developement) build

I have one little-little multiplayer game, that I’am trying to make it work properly.
But the problem is I need to use seamless travel to make everybody load same level. Single process currently not supporting seamless travel, so I decided to package game and use it second process, at least to check if online subsystem works. It works. I can create session, I can connect to it even on same machine.
But there is a fail: packaged project don’t have level that it need to load. It’s gone!
What I see in PIE:

What I see in packaged game:

DM_Minimal is gone. Why? I shouldn’t. If packager puts only one level, so why (on 4.9) little game on android worked with 2 levels? Is it a bug?
Button “Load DM_Minimal” also don’t work. It is using blueprint node “Open level”.