我正在安装 WP MAIL SMTP插件，但显示这些错误。但所有其他插件均已正确安装。仅smtp插件未安装。错误如下...
Warning: require_once(/home/sgroup/public_html/wp-includes/class-phpmailer.php): failed to open stream: Permission denied in /home/sgroup/public_html/wp-content/plugins/post-smtp/Postman/Phpmailer/PostsmtpMailer.php on line 5
Fatal error: require_once(): Failed opening required '/home/sgroup/public_html/wp-includes/class-phpmailer.php' (include_path='.:/opt/cpanel/ea-php71/root/usr/share/pear') in /home/sgroup/public_html/wp-content/plugins/post-smtp/Postman/Phpmailer/PostsmtpMailer.php on line 5