xienwolf
Deity
Well, I just popped those 3 files into a folder called Chest and loaded it into my Assets/Art folder, worked fine.
I am guessing you already have some items added to your Art folder, as I do not have any Structures folder in there, let alone another inside of that. So at least that eliminates some possibilities.
My best guess: There is a limit to how deeply you can Nest a folder. Thus if you moved it back 1 or 2 folders total you should possibly be fine.
Best workaround I can think of: Quit putting things where the computer has any possible pre-conceptions
If you toss things into Assets/Modules then there is guaranteed no limit to your nesting allowance, and the computer doesn't expect any specific structure. Once you have it working, then you can shuffle it into a more "normal" location and at least know that it isn't the files themselves which are the problem, but something in the core program and structure.
EDIT: Just tried it with the exact file structure which you defined yourself as using, and it worked fine. So I got no clue.
I am guessing you already have some items added to your Art folder, as I do not have any Structures folder in there, let alone another inside of that. So at least that eliminates some possibilities.
My best guess: There is a limit to how deeply you can Nest a folder. Thus if you moved it back 1 or 2 folders total you should possibly be fine.
Best workaround I can think of: Quit putting things where the computer has any possible pre-conceptions

EDIT: Just tried it with the exact file structure which you defined yourself as using, and it worked fine. So I got no clue.