はじめまして。
お世話になります。

ゲストで購入する際に、「システムエラーが発生しました。」という画面になり、購入することができません。

EC-CUBEのログを確認しましたら、
プラグインでインストールしている「EC-CUBEペイメントLite4」にてエラーが発生しているようでした。
こちらの原因、対処方法をご教示いただくことはできますでしょうか。


[EC-CUBE] EC-CUBE4.0.3
[レンタルサーバ] レンタルサーバ名
[OS] Linux s210.7artisan.cloud 3.10.0-1062.1.2.el7.x86_64 #1 SMP Mon Sep 30 14:19:46 UTC 2019 x86_64
[PHP] PHP Version 7.3.11
[データベース] MySQL 5.7.27
[WEBサーバ] Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips
[導入プラグインの有無] EC-CUBEペイメントLite4
[カスタマイズの有無] 不明
[現象]エラーになる操作は下記になります。

商品をカートに入れる。
→カートへ進む
→レジに進む
→ゲスト購入
→お客様情報を入力し、「次へ」ボタンを押す。
→「システムエラーが発生しました。」画面になる。


■ログ

[2022-05-15 14:47:37] php.INFO [N/A] [76e157b] [N/A] [Symfony\Component\Debug\ErrorHandler:handleError:528] - User Deprecated: Using the "Twig_Loader_Chain" class is deprecated since Twig version 2.7, use "Twig\Loader\ChainLoader" instead. {"exception":"[object] (ErrorException(code: 0): User Deprecated: Using the \"Twig_Loader_Chain\" class is deprecated since Twig version 2.7, use \"Twig\\Loader\\ChainLoader\" instead. at /home/www/html/vendor/twig/twig/lib/Twig/Loader/Chain.php:7)"} [GET, /products/detail/22281?gclid=EAIaIQobChMI2_6Tjufg9wIVB2oqCh31nQ_HEAAYASAAEgJvqvD_BwE, 122.214.158.210, https://www.google.co.jp/, Mozilla/5.0 (iPhone; CPU iPhone OS 15_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.4 Mobile/15E148 Safari/604.1]
[2022-05-15 14:47:34] app.DEBUG [N/A] [d1732a9] [anon.] [Eccube\Log\Logger:log:68] - Commit executed. [] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:34] app.INFO [N/A] [d1732a9] [anon.] [Eccube\Log\Logger:log:68] - PROCESS END ["shopping"] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:34] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - LOGIC END ["shopping"] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]


[2022-05-15 14:47:34] front.ERROR [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - システムエラーが発生しました。 ["Call to a member function getId() on null","/home/www/html/app/Plugin/EccubePaymentLite4/EventListener/EventSubscriber/Front/Shopping/RemoveRegCreditRadioBtnWhenGuest.php",43,"#0 /home/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(212): Plugin\\EccubePaymentLite4\\EventListener\\EventSubscriber\\Front\\Shopping\\RemoveRegCreditRadioBtnWhenGuest->index(Object(Eccube\\Event\\TemplateEvent), 'Shopping/index....', Object(Symfony\\Component\\EventDispatcher\\ContainerAwareEventDispatcher))\n#1 /home/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(44): Symfony\\Component\\EventDispatcher\\EventDispatcher->doDispatch(Array, 'Shopping/index....', Object(Eccube\\Event\\TemplateEvent))\n#2 /home/www/html/src/Eccube/Twig/Environment.php(48): Symfony\\Component\\EventDispatcher\\EventDispatcher->dispatch('Shopping/index....', Object(Eccube\\Event\\TemplateEvent))\n#3 /home/www/html/vendor/sensio/framework-extra-bundle/EventListener/TemplateListener.php(103): Eccube\\Twig\\Environment->render('Shopping/index....', Array)\n#4 /home/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(212): Sensio\\Bundle\\FrameworkExtraBundle\\EventListener\\TemplateListener->onKernelView(Object(Symfony\\Component\\HttpKernel\\Event\\GetResponseForControllerResultEvent), 'kernel.view', Object(Symfony\\Component\\EventDispatcher\\ContainerAwareEventDispatcher))\n#5 /home/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(44): Symfony\\Component\\EventDispatcher\\EventDispatcher->doDispatch(Array, 'kernel.view', Object(Symfony\\Component\\HttpKernel\\Event\\GetResponseForControllerResultEvent))\n#6 /home/www/html/vendor/symfony/http-kernel/HttpKernel.php(156): Symfony\\Component\\EventDispatcher\\EventDispatcher->dispatch('kernel.view', Object(Symfony\\Component\\HttpKernel\\Event\\GetResponseForControllerResultEvent))\n#7 /home/www/html/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\\Component\\HttpKernel\\HttpKernel->handleRaw(Object(Symfony\\Component\\HttpFoundation\\Request), 1)\n#8 /home/www/html/vendor/symfony/http-kernel/Kernel.php(200): Symfony\\Component\\HttpKernel\\HttpKernel->handle(Object(Symfony\\Component\\HttpFoundation\\Request), 1, true)\n#9 /home/www/html/index.php(76): Symfony\\Component\\HttpKernel\\Kernel->handle(Object(Symfony\\Component\\HttpFoundation\\Request))\n#10 {main}"] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]


[2022-05-15 14:47:34] php.CRITICAL [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Symfony\Component\Debug\ErrorHandler:handleException:580] - Call to a member function getId() on null {"exception":"[object] (Symfony\\Component\\Debug\\Exception\\FatalThrowableError(code: 0): Call to a member function getId() on null at /home/www/html/app/Plugin/EccubePaymentLite4/EventListener/EventSubscriber/Front/Shopping/RemoveRegCreditRadioBtnWhenGuest.php:43)"} [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:34] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - [注文手続] 集計処理を開始します. [null] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:34] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - [注文手続] 受注の初期化処理を開始します. [] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - LOGIC START ["shopping"] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.DEBUG [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - Begin Transaction. [] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - PROCESS START ["shopping"] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [N/A] [d1732a9] [N/A] [Eccube\Log\Logger:log:66] - INIT [] [GET, /shopping, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] app.INFO [N/A] [97f5358] [anon.] [Eccube\Log\Logger:log:68] - PROCESS END ["shopping_nonmember"] [POST, /shopping/nonmember, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [97f5358] [anon.] [Eccube\Log\Logger:log:66] - LOGIC END ["shopping_nonmember"] [POST, /shopping/nonmember, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [97f5358] [anon.] [Eccube\Log\Logger:log:66] - 非会員お客様情報登録完了 [] [POST, /shopping/nonmember, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [97f5358] [anon.] [Eccube\Log\Logger:log:66] - 非会員お客様情報登録開始 [] [POST, /shopping/nonmember, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [97f5358] [anon.] [Eccube\Log\Logger:log:66] - LOGIC START ["shopping_nonmember"] [POST, /shopping/nonmember, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [ke8ek5r2shhg67ua1uij3asmnt] [97f5358] [anon.] [Eccube\Log\Logger:log:66] - PROCESS START ["shopping_nonmember"] [POST, /shopping/nonmember, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]
[2022-05-15 14:47:33] front.INFO [N/A] [97f5358] [N/A] [Eccube\Log\Logger:log:66] - INIT [] [POST, /shopping/nonmember, 118.241.122.135, https://ecshop.pet-coo.com/shopping/nonmember, Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36]

当方でもEC-CUBEペイメントLite4使っていますがゲスト購入はできています。（まだテスト環境ですが）
ですが、EC-CUBEペイメントLite4のイプシロン側、EC-CUBE側にどのような環境設定されてるのかにもよりますし、ここではなく開発元（→イプシロン）に問い合わせされたほうがいいと思いますよ。

ちなみに"ゲスト購入の場合は登録済みのクレジットカードのラジオボタンを表示しない"という処理の中でのエラーっぽいのでそのあたりから調べてもらうことになるんじゃないでしょうか。

回答いただきまして、誠にありがとうございます。
「登録済みのクレジットカードのラジオボタンを表示しない"という処理の中でのエラーっぽい」というのは、ログからおわかりになられたのでしょうか。ログの意味がわからなかったので、大変助かりました。この件も含めてイプシロン側も問い合わせて見るように致します。

[2022-05-15 14:47:34] front.ERROR [ke8ek5r2shhg67ua1uij3asmnt] [d1732a9] [anon.] [Eccube\Log\Logger:log:66] - システムエラーが発生しました。 ["Call to a member function getId() on null","/home/www/html/app/Plugin/EccubePaymentLite4/EventListener/EventSubscriber/Front/Shopping/RemoveRegCreditRadioBtnWhenGuest.php",43,"#0 /home/www/html/vendor/symfony/event-dispatcher/EventDispatcher.php(212):

ってところが目に止まったのでRemoveRegCreditRadioBtnWhenGuest.phpを覗き見したらそう書いてあったというだけです。ちゃんと見てないですよw

イプシロン側”に”問い合わせてくださいね。こちらただの通りすがりの者ですから