Customers Cannot checkout as guest in Magento 2.3

Question

Several of our customers have complained that they cannot checkout as a guest.

The issue seems to have started around the time we upgraded to Magento 2.3.2.

I have tried to checkout as a guest myself and when I click the "Place Order" button I get a blank error message on the page.

Checking in the developer console I also found the following errors displayed:

Failed to load resource: the server responded with a status of 500 (Internal Server Error) /rest/default/V1/guest-carts/JxzHZPwfSjViq24inacrHuFynyOBAOCC/payment-information:1

jquery.js:10254 POST https://www.mywebsite.com/rest/default/V1/guest-carts/JxzHZPwfSjViq24inacrHuFynyOBAOCC/payment-information 500 (Internal Server Error)

I have checked in the Apache logs and found numerous instances of the following error:

AH01071: Got error 'PHP message: PHP Fatal error: Uncaught Error: Call to a member function getCarrier() on boolean in /var/www/vhosts/mywebsite.com/httpdocs/vendor/magento/module-checkout/Model/GuestPaymentInformationManagement.php:196\nStack trace:\n#0 /var/www/vhosts/mywebsite.com/httpdocs/vendor/magento/module-checkout/Model/GuestPaymentInformationManagement.php(154): Magento\Checkout\Model\GuestPaymentInformationManagement->limitShippingCarrier(Object(Magento\Quote\Model\Quote\Interceptor))\n#1 /var/www/vhosts/mywebsite.com/httpdocs/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Checkout\Model\GuestPaymentInformationManagement->savePaymentInformation('HXVzgs4yJY4TuJT...', 'customeremail@gmail.c...', Object(Magento\Quote\Model\Quote\Payment\Interceptor), Object(Magento\Quote\Model\Quote\Address\Interceptor))\n#2 /var/www/vhosts/mywebsite.com/httpdocs/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Checkout\Model\GuestPaymentInformationManagement\Interceptor->___callParent('savePayme...\n', referer: https://www.mywebsite.com/checkout/

A similar issue has been reported in issue 281311 however we do not have the module specified in the answer there activated. So I cannot implement the solution provided.

The Modules we currently have on the site are as follows.

List of enabled modules:

Magento_Store
Magento_AdvancedPricingImportExport
Magento_Directory
Magento_Amqp
Magento_Config
Magento_Theme
Magento_Backend
Magento_Variable
Magento_Eav
Magento_Search
Magento_Backup
Magento_Customer
Magento_AdminNotification
Magento_Authorization
Magento_BundleImportExport
Magento_CacheInvalidate
Magento_Indexer
Magento_Cms
Magento_Security
Magento_GraphQl
Magento_CatalogImportExport
Magento_Catalog
Magento_CatalogInventory
Magento_Rule
Magento_Msrp
Magento_CatalogRule
Magento_CatalogUrlRewrite
Magento_StoreGraphQl
Magento_Widget
Magento_Quote
Magento_SalesSequence
Magento_Payment
Magento_CmsGraphQl
Magento_CmsUrlRewrite
Magento_CmsUrlRewriteGraphQl
Magento_User
Magento_Sales
Magento_Checkout
Magento_EavGraphQl
Magento_ConfigurableProduct
Magento_Contact
Magento_Cookie
Magento_Cron
Magento_CurrencySymbol
Magento_Authorizenet
Magento_Integration
Magento_CustomerGraphQl
Magento_CustomerImportExport
Magento_Deploy
Magento_Developer
Magento_Dhl
Magento_AsynchronousOperations
Magento_DirectoryGraphQl
Magento_Downloadable
Magento_CatalogGraphQl
Magento_ImportExport
Magento_Bundle
Magento_BundleGraphQl
Magento_CatalogSearch
Magento_AdvancedSearch
Magento_Email
Magento_EncryptionKey
Magento_Fedex
Magento_GiftMessage
Magento_GoogleAdwords
Magento_GoogleAnalytics
Magento_Ui
Magento_UrlRewriteGraphQl
Magento_PageCache
Magento_GroupedProduct
Magento_GroupedImportExport
Magento_GroupedCatalogInventory
Magento_GroupedProductGraphQl
Magento_DownloadableImportExport
Magento_AuthorizenetAcceptjs
Magento_InstantPurchase
Magento_Analytics
Magento_CatalogInventoryGraphQl
Magento_Shipping
Magento_LayeredNavigation
Magento_Marketplace
Magento_MediaStorage
Magento_MessageQueue
Magento_ConfigurableImportExport
Magento_MsrpConfigurableProduct
Magento_MsrpGroupedProduct
Magento_Multishipping
Magento_MysqlMq
Magento_NewRelicReporting
Magento_Newsletter
Magento_OfflinePayments
Magento_SalesRule
Magento_GraphQlCache
Magento_Vault
Magento_Paypal
Magento_Captcha
Magento_PaypalCaptcha
Magento_Persistent
Magento_ProductAlert
Magento_ProductVideo
Magento_CheckoutAgreements
Magento_QuoteAnalytics
Magento_QuoteGraphQl
Magento_ReleaseNotification
Magento_Reports
Magento_RequireJs
Magento_Review
Magento_ReviewAnalytics
Magento_Robots
Magento_Rss
Magento_Elasticsearch
MSP_ReCaptcha
Magento_SalesAnalytics
Magento_SalesGraphQl
Magento_SalesInventory
Magento_OfflineShipping
Magento_CatalogRuleConfigurable
Magento_UrlRewrite
Magento_Elasticsearch6
Magento_CustomerAnalytics
Magento_SendFriend
Magento_SendFriendGraphQl
Magento_Signifyd
Magento_Sitemap
Magento_ConfigurableProductGraphQl
Magento_Webapi
Magento_SwaggerWebapi
Magento_SwaggerWebapiAsync
Magento_Swatches
Magento_SwatchesGraphQl
Magento_SwatchesLayeredNavigation
Magento_Tax
Magento_TaxGraphQl
Magento_TaxImportExport
Magento_DownloadableGraphQl
Magento_ThemeGraphQl
Magento_Tinymce3
Magento_Translation
Magento_GoogleOptimizer
Magento_Ups
Magento_SampleData
Magento_CatalogUrlRewriteGraphQl
Magento_CatalogAnalytics
Magento_Usps
Magento_ConfigurableProductSales
Magento_Braintree
Magento_VaultGraphQl
Magento_Version
Magento_Swagger
Magento_WebapiAsync
Magento_WebapiSecurity
Magento_Weee
Magento_WeeeGraphQl
Magento_CatalogWidget
Magento_Wishlist
Magento_WishlistAnalytics
Magento_WishlistGraphQl
Adyen_Payment
Amasty_Base
Amasty_Conditions
Amasty_CommonRules
Amasty_Pgrid
Amasty_ShippingArea
Amasty_ShippingTableRates
Amasty_Shiprestriction
Amasty_Shiprules
Amazon_Core
Amazon_Login
Amazon_Payment
Dotdigitalgroup_Email
Ess_M2ePro
Foregenix_FgxWeb
Infortis_Infortis
Infortis_Brands
Infortis_Cgen
Infortis_Dataporter
Infortis_Base
Infortis_UltraMegamenu
Infortis_UltraSlideshow
Infortis_Ultimo
Magento_PaypalReCaptcha
MSP_TwoFactorAuth
Magenest_Core
Magenest_SagePay
Mageplaza_Core
Mageplaza_Gdpr
Mirasvit_Core
Mirasvit_Report
Mirasvit_Rewards
Moogento_Core
Moogento_License
Moogento_PickPack
Trade_Tform
Vertex_Tax
Wyomind_Core
Wyomind_OrderEraser
Wyomind_OrdersExportTool
Xtento_XtCore
Xtento_CustomTrackers

List of disabled modules:

Magento_Inventory
Magento_InventoryAdminUi
Magento_InventoryApi
Magento_InventoryBundleProduct
Magento_InventoryBundleProductAdminUi
Magento_InventoryCatalog
Magento_InventorySales
Magento_InventoryCatalogAdminUi
Magento_InventoryCatalogApi
Magento_InventoryCatalogSearch
Magento_InventoryConfigurableProduct
Magento_InventoryConfigurableProductAdminUi
Magento_InventoryConfigurableProductIndexer
Magento_InventoryConfiguration
Magento_InventoryConfigurationApi
Magento_InventoryDistanceBasedSourceSelection
Magento_InventoryDistanceBasedSourceSelectionAdminUi
Magento_InventoryDistanceBasedSourceSelectionApi
Magento_InventoryElasticsearch
Magento_InventoryExportStockApi
Magento_InventoryIndexer
Magento_InventorySalesApi
Magento_InventoryGroupedProduct
Magento_InventoryGroupedProductAdminUi
Magento_InventoryGroupedProductIndexer
Magento_InventoryImportExport
Magento_InventoryCache
Magento_InventoryLowQuantityNotification
Magento_InventoryLowQuantityNotificationAdminUi
Magento_InventoryLowQuantityNotificationApi
Magento_InventoryMultiDimensionalIndexerApi
Magento_InventoryProductAlert
Magento_InventoryReservations
Magento_InventoryReservationCli
Magento_InventoryReservationsApi
Magento_InventoryExportStock
Magento_InventorySalesAdminUi
Magento_InventorySalesFrontendUi
Magento_InventorySetupFixtureGenerator
Magento_InventoryShipping
Magento_InventorySourceDeductionApi
Magento_InventorySourceSelection
Magento_InventorySourceSelectionApi
Magento_InventoryShippingAdminUi
Magento_InventoryGraphQl
Klarna_Core
Klarna_Ordermanagement
Klarna_Kp
Temando_Shipping

If anyone could shed some light on this problem or provide instructions on how to find out which module (if any) is causing the problem I would greatly appreciate it.

Answer 1

The issue seems to have now been resolved.

Thanks to @Hassan Al-Jesh and @Mitro for their advice.

It turns out that it was the extension "Shipping Table Rates" by Amasty that was causing the issue.

As I needed this extension to calculate shipping, simply disabling it (as in 281311) was not an option.

The solution was simply to delete all of the extension files (including the base files) and upload the latest version from the Amasty website.

I believe the issue may have been version compatibility as the version of "Shipping Table Rates" I had been using was fairly old and may not have been compatible with the latest Magento 2.3 version.

In any case the upgrade seems to have resolved the issue.