Orsdxy

Magento 2 payment Checkout page keep showing loader. without showing any error on console or in terminal.

It's because none of the payment options will be enabled by default. You can enable with Stores->configuration-> Sales->Payment Methods-> Cash On Delivery Payment.

So for testing purpose, you can enable 'Cash on Delivery' option from admin panel.
Flush the cache and then try again.

If you have made changes in checkout file like override in your custom theme

Magento_Checkout/layout/checkout_index_index.xml

or inside

Magento_Checkout/templates/..

then keep it revert back it will work.

I'm not sure but I think this is the solution for this particular case.

First of all check in console. A error might appear like,

Uncaught TypeError: Argument 1 passed to
MagentoQuoteModelCartTotals::setExtensionAttributes() must be an
instance of MagentoQuoteApiDataTotalsExtensionInterface, instance
of MagentoQuoteApiDataAddressExtension given, called in
/htdocs/magento2.2/vendor/magento/framework/Api/DataObjectHelper.php
on line 125 and defined in
/htdocs/magento2.2/vendor/magento/module-quote/Model/Cart/Totals.php:592

I debugged for quite a while and come the following solution.

• Need to override MagentoQuoteModelCartCartTotalRepository
  

For that, add following in Namespace/Module/etc/di.xml

<preference for="MagentoQuoteModelCartCartTotalRepository" type="NamespaceModuleModelRewriteQuoteCartTotalRepository" />

• Create CartTotalRepository.php at the path NamespaceModuleModelRewriteQuoteCartTotalRepository.php

Paste the following code in CartTotalRepository.php

<?php

/**

 * Copyright © Magento, Inc. All rights reserved.

 * See COPYING.txt for license details.

 */

namespace NamespaceModuleModelRewriteQuote;



use MagentoQuoteApi;

use MagentoQuoteApiCartRepositoryInterface;

use MagentoQuoteApiCartTotalRepositoryInterface;

use MagentoCatalogHelperProductConfigurationPool;

use MagentoFrameworkApiDataObjectHelper;

use MagentoQuoteModelCartTotalsItemConverter;

use MagentoQuoteApiCouponManagementInterface;



/*Added below two lines*/

use MagentoQuoteModelCartTotalsConverter;

use MagentoFrameworkApiExtensibleDataInterface;



/**

 * Cart totals data object.

 * @SuppressWarnings(PHPMD.CouplingBetweenObjects)

 */

class CartTotalRepository extends MagentoQuoteModelCartCartTotalRepository

{

    /**

     * Cart totals factory.

     *

     * @var ApiDataTotalsInterfaceFactory

     */

    private $totalsFactory;



    /**

     * Quote repository.

     *

     * @var MagentoQuoteApiCartRepositoryInterface

     */

    private $quoteRepository;



    /**

     * @var MagentoFrameworkApiDataObjectHelper

     */

    private $dataObjectHelper;



    /**

     * @var ConfigurationPool

     */

    private $itemConverter;



    /**

     * @var CouponManagementInterface

     */

    protected $couponService;



    /**

     * @var TotalsConverter

     */

    protected $totalsConverter;



    /**

     * @param ApiDataTotalsInterfaceFactory $totalsFactory

     * @param CartRepositoryInterface $quoteRepository

     * @param DataObjectHelper $dataObjectHelper

     * @param CouponManagementInterface $couponService

     * @param TotalsConverter $totalsConverter

     * @param ItemConverter $converter

     */

    public function __construct(

        ApiDataTotalsInterfaceFactory $totalsFactory,

        CartRepositoryInterface $quoteRepository,

        DataObjectHelper $dataObjectHelper,

        CouponManagementInterface $couponService,

        TotalsConverter $totalsConverter,

        ItemConverter $converter

    ) {

        $this->totalsFactory = $totalsFactory;

        $this->quoteRepository = $quoteRepository;

        $this->dataObjectHelper = $dataObjectHelper;

        $this->couponService = $couponService;

        $this->totalsConverter = $totalsConverter;

        $this->itemConverter = $converter;

    }



    /**

     * {@inheritDoc}

     *

     * @param int $cartId The cart ID.

     * @return Totals Quote totals data.

     */

    public function get($cartId)

    {

        /** @var MagentoQuoteModelQuote $quote */

        $quote = $this->quoteRepository->getActive($cartId);

        if ($quote->isVirtual()) {

            $addressTotalsData = $quote->getBillingAddress()->getData();

            $addressTotals = $quote->getBillingAddress()->getTotals();

        } else {

            $addressTotalsData = $quote->getShippingAddress()->getData();

            $addressTotals = $quote->getShippingAddress()->getTotals();

        }

        //Added New Line Here

        unset($addressTotalsData[ExtensibleDataInterface::EXTENSION_ATTRIBUTES_KEY]);

        /** @var MagentoQuoteApiDataTotalsInterface $quoteTotals */

        $quoteTotals = $this->totalsFactory->create();

        $this->dataObjectHelper->populateWithArray(

            $quoteTotals,

            $addressTotalsData,

            MagentoQuoteApiDataTotalsInterface::class

        );

        $items = ;

        foreach ($quote->getAllVisibleItems() as $index => $item) {

            $items[$index] = $this->itemConverter->modelToDataObject($item);

        }

        $calculatedTotals = $this->totalsConverter->process($addressTotals);

        $quoteTotals->setTotalSegments($calculatedTotals);



        $amount = $quoteTotals->getGrandTotal() - $quoteTotals->getTaxAmount();

        $amount = $amount > 0 ? $amount : 0;

        $quoteTotals->setCouponCode($this->couponService->get($cartId));

        $quoteTotals->setGrandTotal($amount);

        $quoteTotals->setItems($items);

        $quoteTotals->setItemsQty($quote->getItemsQty());

        $quoteTotals->setBaseCurrencyCode($quote->getBaseCurrencyCode());

        $quoteTotals->setQuoteCurrencyCode($quote->getQuoteCurrencyCode());

        return $quoteTotals;

    }

}

I have made 2 modifications in the file.
1. Simply added 2 lines on line number 17 & 18.
2. Added 1 line on line number 102.