Changing AttributeModifiers of Weapons and Armor in Minecraft(Java)

Question

I am using Java with Maven and Spigot-API(1.19.4) to create a plugin which enhances item modifiers for weapons and armor if the enchantment is succesful(+5% per level, for total of 20 levels). The issue is, for some reason it does not apply the changes to the item. What could be an issue here? Do i have to maybe return some value in this method?(new to this) Here is the apply method:

    private void applyEffects(ItemStack item, int whetLevel) {
    double multiplier = 1 + (whetLevel * 0.05);
    ItemMeta itemMeta = item.getItemMeta();
    if (itemMeta == null) return;
    if(isWeapon(item)){
    AttributeModifier currentAttackDamageModifier = null;
    AttributeModifier currentAttackSpeedModifier = null;
    if(itemMeta.getAttributeModifiers(Attribute.GENERIC_ATTACK_DAMAGE) != null){
        for(AttributeModifier modifier : itemMeta.getAttributeModifiers(Attribute.GENERIC_ATTACK_DAMAGE)){
            currentAttackDamageModifier = modifier;
            break;
        }
    }
    if(itemMeta.getAttributeModifiers(Attribute.GENERIC_ATTACK_SPEED) != null){
        for(AttributeModifier modifier : itemMeta.getAttributeModifiers(Attribute.GENERIC_ATTACK_SPEED)){
            currentAttackSpeedModifier = modifier;
            break;
        }
    }
    // Remove existing attribute modifiers to avoid stacking modifiers
    for (Attribute attribute : Attribute.values()) {
        itemMeta.removeAttributeModifier(attribute);
    }
    if(currentAttackDamageModifier != null){
        AttributeModifier updatedAttackDamageModifier = new AttributeModifier(
            currentAttackDamageModifier.getUniqueId(),
            currentAttackDamageModifier.getName(),
            currentAttackDamageModifier.getAmount()*multiplier,
            currentAttackDamageModifier.getOperation(),
            currentAttackDamageModifier.getSlot()
        );
        itemMeta.addAttributeModifier(Attribute.GENERIC_ATTACK_DAMAGE, updatedAttackDamageModifier);
    }
    if(currentAttackSpeedModifier != null){
        AttributeModifier updatedAttackSpeedModifier = new AttributeModifier(
            currentAttackSpeedModifier.getUniqueId(),
            currentAttackSpeedModifier.getName(),
            currentAttackSpeedModifier.getAmount()*multiplier,
            currentAttackSpeedModifier.getOperation(),
            currentAttackSpeedModifier.getSlot()
        );
        itemMeta.addAttributeModifier(Attribute.GENERIC_ATTACK_SPEED, updatedAttackSpeedModifier);
    }
}
if(isArmor(item)){
    AttributeModifier currentArmorModifier = null;
    AttributeModifier currentArmorToughnessModifier = null;
    if(itemMeta.getAttributeModifiers(Attribute.GENERIC_ARMOR) != null){
        for(AttributeModifier modifier : itemMeta.getAttributeModifiers(Attribute.GENERIC_ARMOR)){
            currentArmorModifier = modifier;
            break;
        }
    }
    if(itemMeta.getAttributeModifiers(Attribute.GENERIC_ARMOR_TOUGHNESS) != null){
        for(AttributeModifier modifier : itemMeta.getAttributeModifiers(Attribute.GENERIC_ARMOR_TOUGHNESS)){
            currentArmorToughnessModifier = modifier;
            break;
        }
    }
    // Remove existing attribute modifiers to avoid stacking modifiers
    for (Attribute attribute : Attribute.values()) {
        itemMeta.removeAttributeModifier(attribute);
    }
    if(currentArmorModifier != null){
        AttributeModifier updatedArmorModifier = new AttributeModifier(
            currentArmorModifier.getUniqueId(),
            currentArmorModifier.getName(),
            currentArmorModifier.getAmount()*multiplier,
            currentArmorModifier.getOperation(),
            currentArmorModifier.getSlot()
        );
        itemMeta.addAttributeModifier(Attribute.GENERIC_ARMOR, updatedArmorModifier);
    }
    if(currentArmorToughnessModifier != null){
        AttributeModifier updatedArmorToughnessModifier = new AttributeModifier(
            currentArmorToughnessModifier.getUniqueId(),
            currentArmorToughnessModifier.getName(),
            currentArmorToughnessModifier.getAmount()*multiplier,
            currentArmorToughnessModifier.getOperation(),
            currentArmorToughnessModifier.getSlot()
        );
        itemMeta.addAttributeModifier(Attribute.GENERIC_ARMOR_TOUGHNESS, updatedArmorToughnessModifier); 
    }
}
item.setItemMeta(itemMeta);
}