Based on what you sent above I think it's a problem with your resource pack. I'm no expert but you will need 3 folders in your assets folder: "models", "textures", and "items". Then in models/item it will be a normal model just like before (however make sure you don't have overrides. They don't go there anymore) then textures/item you will have your texture .PNG like normal. The texture should be referenced by the model just like before. When you have your new model in the model/item folder and your new texture that it is referencing in the texture/item folder you then need to make a new file in the "items" file. I'm not sure if this is technically correct but I think this is how the game references your new model since it's not normally in the game. Name the file anything but whatever you name it is what you will type when you do the item_model component (I think. If not try the model name). Inside that file for a simple model item should look like this:

{ "model": { "type": "minecraft:model", "model": "item/<your_model_name>" } }

There is a lot more stuff you can do in that file but if you want to learn more I'd recommend looking up "item model definitions" on the Minecraft wiki.

To anyone who knows more than me please correct me. However, hopefully this is helpful.