This should help you with troubleshooting.
Since you have the game fully packaged you can actually run the game from Visual Studio as if it was running in that packaged directory.
In visual studio, switch your project configuration from Development Editor to a non-editor one, like Development (try that first) or Shipping.
Then, add the -basedir launch command-line parameter, like this:
-basedir=C:\PathToYourGameFolder\Binaries\Win64.
Now you can compile the game and run it but using the pak file, configs and everything as if it was running in that game folder, and you can debug exactly what is happening.