That's really odd, what does the error say? Could you check if it's a permission problem? If the user is using a guest account or something that doesn't have write permission to wherever the save directory is located something like this might happen.
Basically it's saying that no save location is found and I don't believe that's your game's fault because it's happened on other renpy games as well. I'm just unsure of how to fix the error.
Yikes! Yeah, I've seen people have this issue on other renpy games before. Could you try this? 1) Delete the game folder 2) Delete your saves (they are usually in your /user/ folder) 3) Re-Extract the game into a new folder
I don't know if your still on here or making video games, (30 days can change a lot) but is there anyway I could get in contact with you like email or social media? I have visions for what you could create