The above forums post link contains how to get nDisplay to work correctly in a shipping build when running with/with-out Switchboard.
Basically the problem is that you can’t modify what game engine, network driver, ect classes Unreal will run via command line as these are dev only commands. Since Switchboard tells Unreal how to utilize nDisplay by changing the game engine/network driver/ect via command line, it will ignore these commands and start Unreal up utilizing the standard classes, thus never act like an nDisplay setup.
Also, if you use those same command line arguments via some type of .bat file or other way to execute your Shipping packaged game, you will run into the same issue.
The fix is to package the game with DefaultEngine.ini changes in that file so that the Shipping packaged project will just start with nDisplay changes by default or change your UserEngine.ini to change what classes Unreal with startup as at that executing point.