Packaging a Windows game from Editor built from sources produces an UE4Game.exe placed in [project dir]\WindowsNoEditor\Engine\Binaries\Win64 folder which application is raises a Message window (image attached) then quits.
Renaming the UE4Game.exe to TappyChicken.exe gets the project run properly.
Have you attempted re-downloading the project to see if it was a corrupted or missing file? Further does this only happen with or does it happen with other projects as well?
While I could not reproduce your bug, I am putting in a bug report with this post attached to it so we can address this issue. Thank you and have a great day!
This was a bug with the source build in 4.0, and only manifests when packaging a content-only project.
The version of the editor that we ship through the launcher is compiled using the UE_ROCKET define, which adds -Rocket to the editor’s command line. We use this parameter to control behaviors that are common to people who aren’t building the editor themselves, and accidentally lumped support for packaging of content-only projects into this category.