Capability disappearing/not reattaching

[AMOnDuck]

I have a cooldown capability that I want to attach to items with specific enchants and it attaches fine when loading in but when you drop the item or enchant an existing item with the target enchant it won't attach.
Here's the relevant code

    @Mod.EventBusSubscriber(modid = PondWeaponMod.MODID, bus = Mod.EventBusSubscriber.Bus.FORGE)
    public static class Events {
        @SubscribeEvent
        public static void attachCapabilityEnchantedItemEvent(AttachCapabilitiesEvent<ItemStack> event) {
            if(event.getObject() instanceof ItemStack) {
                if (!event.getObject().getStack().getEnchantmentTagList().isEmpty()){
                    System.out.println(event.getObject().getStack().getEnchantmentTagList());
                    if (EnchantmentHelper.getEnchantments(event.getObject().getStack()).get(ModEnchantments.thunder) != null) {
                        event.addCapability(new ResourceLocation(PondWeaponMod.MODID, "cooldown"), new CooldownCapability());
                    }
                }
            }
        }
    }

Any ideas on how to properly handle this?

Edited November 19, 2021 by AMOnDuck
spelling error

[Alpvax]

Always attach the capability provider to the item and add the check to the getCapability method of the provider instead. AttachCapabilitiesEvent is only fired when items are created

[AMOnDuck]

So I should attach the capability to all itemstacks?

[Alpvax]

You should attach it to any itemstacks which might use it at any point in the future (so if is based on an enchantment, you only have to attach it to items which can be affected by that enchantment for example)

[Draco18s]

Note that enchanting an existing item does not call AttachCapabilities because it's adding data to an existing item stack, not creating a new one.