Test Enviroment not registering changes to workspace

So I am working on a mod and recently added several new mod elements (An Item, a Potion Effect and a simple procedure.) However when I enter the game (Testing in MCreator) the Item is not in the creative tabs and I can't get it via /give. I tried to give myself the potion effect and it also doesn't work. When I change any other mod elements the changes appear in the workspace editor, but not in the game. I can still get any Item or other in game Object created previously but they remain as they were earlier with no changes. New Items don't show up at all. No idea why this is happening but it makes MCreator unusable.