Missing Textures (Elements)

[MooshroomStatus]

So I was reading another post about this, and I'm sorry to say that it actually didn't solve anything. So I'm trying to design custom hats for a server. To do so, I'm using items and making 3D models out of them. This method USED to work on CubikPRO until they downgraded and became Cubik Studio.

Here's the fast process;
I made a .png image to replace a typically unused block in minecraft (I generally used command blocks) to serve as a color template.
I then proceed to make my hat. In doing so, I use elements, and with these elements, I dedicate that .png I made earlier to being my texture that gets used.
I select the UV mappings to be used as colors on my model.
When the model is finished, I export it as an item (a feather per say).
I proceed to .minecraft/resourcepacks/myresourcepack/assets/minecraft/models/item and then add the .JSON (feather in this example) to the folder.
I would reload my resource packs and BOOM, my 3D model was there.

For some reason now, this no longer works. the JSON formatting must've gotten messed up on the change from CubikPRO to CubikStudio. Whenever I go in game, I get the pink and black square block instead of what used to become my 3D model.
Where is my error in this? (I know it still works in 1.11 because I did it before my CubikPRO became CubikStudio)

[Sphax]

You'll have to share here the JSON which produces a pink/black cube in game so we can help