I wish to print when an order begins processing, not when it is paid

By default, orders made with “manual” payment methods (like cash, cheque or bank transfer) are printed as soon as they are placed. Orders made with automatic methods (which means that the payment gateway can inform WooCommerce that a payment has been made) are not printed when placed, but when the payment signal is made (in WordPress/WooCommerce developer terms, this means “when the ‘payment_complete’ action is called).

If the signal never comes, then it’s best to investigate why not. However, you can, if you prefer, instead make your orders print when they are placed instead, by adding this snipped as an mu-plugin (i.e. add this as a file ending in .php in wp-content/mu-plugins, e.g. wp-content/mu-plugins/print-orders.php):

<?php add_filter('woocommerce_print_orders_print_order_upon_processed', '__return_true');

Posted in: WooCommerce Google Cloud Print Automatic Printing