Did you add line to my version to trigger the delegate?
pStreaming->OnLevelLoaded.AddDynamic(, &ADreamProjectGameMode::OnLevelLoaded);
it would go here:
StreamingLevel->LevelColor = FColor::MakeRandomColor();
StreamingLevel->bShouldBeLoaded = true;
StreamingLevel->bShouldBeVisible = true;
StreamingLevel->bShouldBlockOnLoad = false;
StreamingLevel->bInitiallyLoaded = true;
StreamingLevel->bInitiallyVisible = true;