My Noob Creations

The normal map is an additional map done in greyscale that, when combined in the game with the diffuse image you put your cardigan texture on, helps to increase the illusion that the garment details are 3D.

Sims 4 Studio has two choices when working with CAS items: 1. Recoloring and 2. Creating a new mesh. For most recoloring purposes using the Recoloring feature is sufficient and it makes your .package leaner to do the recolor this way so it's better to do it that way if you can. To me, your project looks fine as a simple recolor and I think it's kind of ridiculous that your item was rejected.

That said, you have added intricate detailing (and it looks beautiful) where there was none before. You can increase the realism of that detailing through the use of a bump map (aka normal map). EA has included the normal map in the GEOM resource. This resource is the mesh itself and, for simple recolors Studio does not pull the meshes into the .package because this it is unnecessary .package bloat to include meshes in a recolor unless you specifically need the bump map for your project in which case there is no avoiding the bloat because of how EA constructed the .package.

The solution is to reclone the same exact cardigan you used the first time using the Create 3D mesh button instead of the recolor button. Import your images as usual. You will see a Meshes tab that wasn't present when you chose to do this as a Recolor but you can ignore that because you aren't planning on changing the mesh. After you have imported your textures click the Warehouse tab. Scroll through the images until you find a greyscale one. This is the one you need to edit to make your bump. You will want to make your bump the same size and you will want it to be based on your diffuse image.

I don't use Photoshop but I found this video tutorial that looks like it should do the trick to show you how to do this:

Follow that and where he saves it as a .targa you will save it as a .dds. Then import that .dds back into the Warehouse to overwrite the EA bump. If you continue to watch the tutorial after that save step you will see him import his targa into Maya where he has a model already displaying his diffuse. He loads the bump in and renders the model which is what the game will do with your bump. He will show what the model looks like without a bump and the improvement in appearance when rendered with the bump. This should give you an idea of what you're aiming for in terms of appearance.

I hope this helps but if it isn't enough information please open a thread in the Creator Help section so your lovely work on the cardigan isn't in vain.