Game works in editor but not packaged

I finished development and can play the game - but only in editor. Project builds without any errors, yet it is unplayable, features doesn’t work as they should.
If there are no build errors, shouldn’t built game = game in editor?

If I run it in standalone mode, will it some way help with the built project?

Which features are not working for you? I’m having similar issues, but it’s mainly on multiplayer (when 2 instances of the game are running).

Cannot join sessions.

its not related to these (already checked them)

shouldn’t built game = game in editor?

Apparently no. Most of the time editor version will work fine but the build version can simply crash.
You need to provide more info like crash dump file etc.

You could try to run game in Standalone mode.

Networking Overview

Client-Server Model