Critical Error when generating eBook

In the current version of eBook Store and WooCommerce I have the problem that when a new order goes into the order status “completed”, no eBook is generated.

If I manually set the order to completed, a critical error appears. No email with the eBook goes out.

The following error message appears in the error log:

Fehler-Details
==============
Ein Fehler vom Typ E_ERROR wurde in der Zeile 3193 der Datei
/www/htdocs/w011599c/shop.tanz-zentrale.de/wp-content/plugins/ebook-store/functions.php
verursacht. Fehlermeldung: Uncaught TypeError: Unsupported operand
types: string * float in
/www/htdocs/w011599c/shop.tanz-zentrale.de/wp-content/plugins/ebook-store/functions.php:3193
Stack trace:
#0 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-content/plugins/ebook-store/functions.php(3147):
ebook_store_woocommerce_email_delivery(21480)
#1 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/class-wp-hook.php(326):
ebook_store_woocommerce_email_delivery_completed(21480,
Object(Automattic\WooCommerce\Admin\Overrides\Order))
#2 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/class-wp-hook.php(348):
WP_Hook->apply_filters(”, Array)
#3 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/plugin.php(517):
WP_Hook->do_action(Array)
#4 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-content/plugins/woocommerce/includes/class-wc-order.php(438):
do_action(‘woocommerce_ord…’, 21480,
Object(Automattic\WooCommerce\Admin\Overrides\Order), Array)
#5 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-content/plugins/woocommerce/includes/class-wc-order.php(272):
WC_Order->status_transition()
#6 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-content/plugins/woocommerce/includes/admin/meta-boxes/class-wc-meta-box-order-data.php(767):
WC_Order->save()
#7 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/class-wp-hook.php(326):
WC_Meta_Box_Order_Data::save(21480)
#8 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/class-wp-hook.php(348):
WP_Hook->apply_filters(NULL, Array)
#9 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/plugin.php(517):
WP_Hook->do_action(Array)
#10 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-content/plugins/woocommerce/includes/admin/class-wc-admin-meta-boxes.php(263):
do_action(‘woocommerce_pro…’, 21480, Object(WP_Post))
#11 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/class-wp-hook.php(326):
WC_Admin_Meta_Boxes->save_meta_boxes(21480, Object(WP_Post))
#12 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/class-wp-hook.php(348):
WP_Hook->apply_filters(”, Array)
#13 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/plugin.php(517):
WP_Hook->do_action(Array)
#14 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/post.php(5060):
do_action(‘save_post’, 21480, Object(WP_Post), true)
#15 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-includes/post.php(5162):
wp_insert_post(Array, false, true)
#16 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-admin/includes/post.php(453):
wp_update_post(Array)
#17 /www/htdocs/w011599c/shop.tanz-zentrale.de/wp-admin/post.php(227):
edit_post()
#18 {main}
  thrown

The current eBook Store version is 5.8007, currenct WooCommerce version is 9.8.1. PHP memory limit is set to 512 MB and we are using PHP 8.2. We are using Elementor Hello Theme in its current version.