Woocommerce Email don’t sent to customer

HiTeam Villatheme,

I just purchased you premium plugin for our site, but during the test, I found when we active the plugin, woocommerce don’t send email to customer, and we only receive the woocommerce admin email (new order, failed order, cancelled order), that means, all of other customer emails can’t send by woocommerce.

At the same time, I found fatal errors like below after active the plugin :

CRITICAL Uncaught TypeError: Pelago\Emogrifier\CssInliner::inlineCss(): Argument #1 ($css) must be of type string, null given, called in /home/our server name/our domain name/wp-content/plugins/woocommerce/includes/emails/class-wc-email.php on line 613 and defined in /home/our server name/our domain name/wp-content/plugins/woocommerce/vendor/pelago/emogrifier/src/CssInliner.php:169
Stack trace:
#0 /home/our server name/our domain name/wp-content/plugins/woocommerce/includes/emails/class-wc-email.php(613): Pelago\Emogrifier\CssInliner->inlineCss()
#1 /home/our server name/our domain name/wp-content/plugins/woocommerce/includes/emails/class-wc-email.php(701): WC_Email->style_inline()
#2 /home/our server name/our domain name/wp-content/plugins/woocommerce/includes/emails/class-wc-email-customer-invoice.php(139): WC_Email->send()
#3 /home/our server name/our domain name/wp-content/plugins/woocommerce/includes/class-wc-emails.php(374): WC_Email_Customer_Invoice->trigger()
#4 /home/our server name/our domain name/wp-content/plugins/woocommerce/includes/admin/meta-boxes/class-wc-meta-box-order-actions.php(139): WC_Emails->customer_invoice()
#5 /home/our server name/our domain name/wp-includes/class-wp-hook.php(324): WC_Meta_Box_Order_Actions::save()
#6 /home/our server name/our domain name/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#7 /home/our server name/our domain name/wp-includes/plugin.php(517): WP_Hook->do_action()
#8 /home/our server name/our domain name/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/Edit.php(303): do_action()
#9 /home/our server name/our domain name/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/Edit.php(152): Automattic\WooCommerce\Internal\Admin\Orders\Edit->handle_order_update()
#10 /home/our server name/our domain name/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/PageController.php(350): Automattic\WooCommerce\Internal\Admin\Orders\Edit->setup()
#11 /home/our server name/our domain name/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/PageController.php(366): Automattic\WooCommerce\Internal\Admin\Orders\PageController->prepare_order_edit_form()
#12 /home/our server name/our domain name/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/PageController.php(167): Automattic\WooCommerce\Internal\Admin\Orders\PageController->setup_action_edit_order()
#13 [internal function]: Automattic\WooCommerce\Internal\Admin\Orders\PageController->handle_load_page_action()
#14 /home/our server name/our domain name/wp-content/plugins/woocommerce/src/Internal/Traits/AccessiblePrivateMethods.php(158): call_user_func_array()
#15 /home/our server name/our domain name/wp-includes/class-wp-hook.php(324): Automattic\WooCommerce\Internal\Admin\Orders\PageController->__call()
#16 /home/our server name/our domain name/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#17 /home/our server name/our domain name/wp-includes/plugin.php(517): WP_Hook->do_action()
#18 /home/our server name/our domain name/wp-admin/admin.php(237): do_action()
#19 {main}
thrown in /home/our server name/our domain name/wp-content/plugins/woocommerce/vendor/pelago/emogrifier/src/CssInliner.php on line 169

Could you please help me to resolve this problem, it is urgent.

Thank you for your help in advance.
Laurent