Keep in mind that when it comes to UE4 modding, if the intention is to have your users create mods for your game, you’ll need to give them an editor version of your game. A good example of this is Ark: Survival Evolved. As seen in the Epic Games Launcher, you would need to download the Ark Dev Kit to mod the game. You add your mod content, cook the game first, then cook your mod, and then distribute that mod. There are general questions/answers about UE4 modding here:
As far as getting this working, just to have a completely controlled case down, what happens if you open the “PackagedSampleGame” folder from the tutorial’s assets, run “ModSampleGame.exe” and then type “open ModExampleMap” into the console?