[EC-CUBE] EC-CUBE4.1.2
[レンタルサーバ] Xserver
[OS] 使用しているOS名、バージョン
[PHP] 7.4
[データベース] mysql5.7


現状4.0で稼働しております。
有料プラグインを購入してインストールしております。

レンタルサーバーを変更するために、EC-CUBEのバージョンを4.1にします。
（プラグインが4.0、4.1対応の為、このバージョンにしました）
プラグイン会社様には、その旨を伝えOKをいただいております。

で、レンタルサーバーにEC-CUBE4.1をインストールしました
そのあと、プラグインをインストールすると、以下のエラーになりインストールできません。

[11.8MiB/1.74s] Using version ^1.1 for ec-cube/deliveryplus4
[11.9MiB/1.74s] ./composer.json has been updated
[13.8MiB/1.94s] Running composer update ec-cube/deliveryplus4 --with-dependencies
[16.5MiB/1.97s] Loading composer repositories with package information
[18.2MiB/2.97s] <warning>Dependency ec-cube/plugin-installer is also a root requirement. Package has not been listed as an update argument, so keeping locked at old version. Use --with-all-dependencies (-W) to include root dependencies.</warning>
[18.4MiB/2.99s] Updating dependencies
[20.0MiB/3.06s] Lock file operations: 1 install, 0 updates, 0 removals
[20.0MiB/3.06s] - Locking ec-cube/deliveryplus4 (1.1.6)
[19.2MiB/3.10s] Writing lock file
[19.2MiB/3.10s] Installing dependencies from lock file
[22.0MiB/3.12s] Package operations: 1 install, 0 updates, 0 removals
[22.0MiB/3.12s] - Downloading ec-cube/deliveryplus4 (1.1.6)
[22.0MiB/4.35s] - Installing ec-cube/deliveryplus4 (1.1.6): Extracting archive
[22.8MiB/5.44s] <warning>Package doctrine/doctrine-cache-bundle is abandoned, you should avoid using it. No replacement was suggested.</warning>
[22.8MiB/5.44s] <warning>Package doctrine/reflection is abandoned, you should avoid using it. Use roave/better-reflection instead.</warning>
[22.8MiB/5.44s] <warning>Package easycorp/easy-log-handler is abandoned, you should avoid using it. No replacement was suggested.</warning>
[22.8MiB/5.44s] <warning>Package setasign/fpdi-tcpdf is abandoned, you should avoid using it. No replacement was suggested.</warning>
[22.8MiB/5.44s] <warning>Package swiftmailer/swiftmailer is abandoned, you should avoid using it. Use symfony/mailer instead.</warning>
[22.8MiB/5.44s] <warning>Package symfony/inflector is abandoned, you should avoid using it. Use EnglishInflector from the String component instead.</warning>
[22.8MiB/5.44s] <warning>Package twig/extensions is abandoned, you should avoid using it. No replacement was suggested.</warning>
[22.8MiB/5.44s] <warning>Package fzaninotto/faker is abandoned, you should avoid using it. No replacement was suggested.</warning>
[22.8MiB/5.44s] <warning>Package phpunit/php-token-stream is abandoned, you should avoid using it. No replacement was suggested.</warning>
[22.8MiB/5.44s] Generating optimized autoload files
[43.7MiB/15.23s] composer/package-versions-deprecated: Generating version class...
[43.7MiB/15.23s] composer/package-versions-deprecated: ...done generating version class
[43.7MiB/15.27s] Carbon 1 is deprecated, see how to migrate to Carbon 2.
[43.7MiB/15.27s] https://carbon.nesbot.com/docs/#api-carbon-2
[43.7MiB/15.27s] You can run './vendor/bin/upgrade-carbon' to get help in updating carbon and other frameworks and libraries that depend on it.
[27.9MiB/15.27s] 103 packages you are using are looking for funding.
[27.9MiB/15.27s] Use the `composer fund` command to find out more!
[28.5MiB/15.29s]
[28.5MiB/15.30s] Run composer recipes at any time to see the status of your Symfony recipes.
[28.5MiB/15.30s]
[28.6MiB/18.24s] Memory usage: 28.61MiB (peak: 60.16MiB), time: 18.24s

他のプラグインもあるのですが、同じようなエラーになります。
原因と、対処方法を教えてください。

上記のログにはエラーレベルのログは出力されていないようです。
admin- のログファイルを確認してみてください。

----------------
EC-CUBE 《プラチナ》ランクパートナー
トエビス株式会社　田中 宏典
EC-CUBEの機能やデザインのカスタマイズ承ります。