Erro ao enviar notas em encomendas

Olá,
temos tido este erro que n?o nos permite efetuar “nota de encomenda para o cliente” a serem enviadas com notifica??o para o cliente. O erro n?o ocorre ao desativar o vosso plugin.

Este é o log do woocommerce do erro:

2023-06-15T14:04:22+00:00 CRITICAL Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function "lusopaygateway_lang_notes" not found or invalid function name in --------/wp-includes/class-wp-hook.php:308
Stack trace:

0 --------/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()

1 --------/wp-includes/plugin.php(517): WP_Hook->do_action()

2 --------/wp-content/plugins/woocommerce/includes/class-wc-order.php(1918): do_action()

3 --------/wp-content/plugins/woocommerce/includes/class-wc-ajax.php(1521): WC_Order->add_order_note()

4 --------/wp-includes/class-wp-hook.php(308): WC_AJAX::add_order_note()

5 --------/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()

6 --------/wp-includes/plugin.php(517): WP_Hook->do_action()

7 --------/wp-admin/admin-ajax.php(188): do_action()

8 {main}

thrown em --------/wp-includes/class-wp-hook.php na linha 308