1.20.4 Creative Mode Tab doesn't display 1.20.4

[StrangePerson]

Hey, 

I tried to create a Creative Mode Tab but in the game only the arrows appear to go to the next "page" but there is no tab on the next page. I created and registered the tab as explained in the forge docs. Does anyone have similar problems? Could be a bug. If it isn't a bug, where could the error be?

 public static final DeferredRegister<CreativeModeTab> TAB = DeferredRegister.create(Registries.CREATIVE_MODE_TAB, MODID);

    public static final RegistryObject<CreativeModeTab> TEST_TAB = TAB.register("test_tab",
            () -> CreativeModeTab.builder()
                    .title(Component.translatable("itemGroup.test_tab"))
                    .icon(() -> ItemInit.COBALT_INGOT.get().getDefaultInstance())
                    .build());

That's how I registered it:

ClassName.TAB.register(modEventBus);

Ingame it looks like this:

Thank you for your help

Edited April 7 by StrangePerson

[Ensamisten]

You'll need to fill the tab with registered items or blocks... it can't be empty.

See here this link.

[StrangePerson]

I added items to the tab but with the BuildCreativeModeTabContentsEvent. Does it matter?