Shipping Method not loading in Case of configurable Products

Hi I am trying add an extra fee to the order using a product custom attribute. however this is working great but in case if the cart has

2 Simple products – working

1 simple and 1 configurable products – shipping method does not load.

below is my code please suggest something:-

use MagentoSalesApiDataOrderItemInterface;
use MagentoSalesApiOrderItemRepositoryInterface;
class GetAllRates{
    protected $_logger;
    protected $cart;
    private $productRepository;
    protected $orderItemRepository;
    private $quoteItemFactory;
    private $itemResourceModel;


    public function __construct(
        PsrLogLoggerInterface $logger,
        MagentoCheckoutModelCart $cart,
        MagentoCatalogApiProductRepositoryInterface $productRepository,
        MagentoQuoteModelQuoteItemFactory $quoteItemFactory,
        MagentoQuoteModelResourceModelQuoteItem $itemResourceModel
    )
    {
        $this->_logger = $logger;
        $this->cart = $cart;
        $this->productRepository = $productRepository;
        $this->quoteItemFactory = $quoteItemFactory;
        $this->itemResourceModel = $itemResourceModel;
    }

    public function afterGetAllRates($subject, $result)
    {
        $writer = new ZendLogWriterStream(BP . '/var/log/templog.log');
        $logger = new ZendLogLogger();
        $logger->addWriter($writer);
        
        foreach ($result as $key => $rate) {
            $price = $rate->getCost();

            $carrier = $rate->getCarrier();
            $price2 = $rate->getPrice();
            
            $cart = $this->cart->getQuote()->getAllItems();
            foreach($cart as $item) {
            $product_id= $item->getProductId();
            $objectManager = MagentoFrameworkAppObjectManager::getInstance();
            $product = $objectManager->get('MagentoCatalogModelProduct')->load($product_id);
            $FixedShippingCost = $product ->getData('fixed_shippingcost');
            $logger->info("fixedshippingcost".json_encode($FixedShippingCost)); //log print
            }
            

            if($carrier == 'fedexseconddaydelivery'){
                if($rate->getCost()==$rate->getPrice()){
                    $shippingCost= $FixedShippingCost + $price;
                    $rate->setPrice($shippingCost);  
                }
            }
     
            if ($rate->getIsDisabled()) {
                unset($result($key));
            }   
        }
        return $result;
    }
}

InstallData.php

use MagentoEavSetupEavSetup;
use MagentoEavSetupEavSetupFactory;
use MagentoFrameworkSetupInstallDataInterface;
use MagentoFrameworkSetupModuleContextInterface;
use MagentoFrameworkSetupModuleDataSetupInterface;
class InstallData implements InstallDataInterface
{
    private $eavSetupFactory;
    public function __construct(EavSetupFactory $eavSetupFactory)
    {
        $this->eavSetupFactory = $eavSetupFactory;
    }
    public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
    {
        $eavSetup = $this->eavSetupFactory->create(('setup' => $setup));
        $eavSetup->addAttribute(
            MagentoCatalogModelProduct::ENTITY,
            'fixed_shippingcost',
            (
                'group' => 'Product Details',
                'type' => 'varchar',
                'backend' => '',
                'frontend' => '',
                'sort_order' => 50,
                'label' => 'Fixed Shipping Cost',
                'input' => 'text',
                'class' => '',
                'source' => '',
                'global' => MagentoEavModelEntityAttributeScopedAttributeInterface::SCOPE_GLOBAL,
                'visible' => true,
                'required' => false,
                'user_defined' => false,
                'default' => '',
                'searchable' => false,
                'filterable' => false,
                'comparable' => false,
                'visible_on_front' => false,
                'used_in_product_listing' => true,
                'unique' => false,
                'apply_to'=>'simple,configurable,bundle,grouped'
            )
        );
    }
}