Have the same problem since updating to Woocommerce 4.4.1 (live site https://4boards.co.uk/) and Woocommerce 4.5.0 (Staging site https://staging-laqaxewe.kinsta.cloud/)
The error appears in the Kinsta site Error Log accessible through the host Dashboard.
2020/09/09 10:17:41 [error] 74862#74862: *18242 FastCGI sent in stderr: “PHP message: The WC_Abstract_Legacy_Order::get_product_from_item function is deprecated since version 4.4.0. Replace with $item->get_product()” while reading response header from upstream, client: 217.44.21.244, server: staging-laqaxewe.kinsta.cloud, request: “GET /wp-admin/admin-ajax.php?print-order=34357&print-order-type=delivery-note&action=print_order HTTP/1.0”, upstream: “fastcgi://unix:/var/run/php7.4-fpm-laqaxewe.sock:”, host: “staging-laqaxewe.kinsta.cloud”, referrer: “https://staging-laqaxewe.kinsta.cloud/wp-admin/edit.php?post_type=shop_order”
PHP versions – Live 7.3 and Staging 7.4 – WordPress 5.5.1
Hope this helps
Bob – 4boards.co.uk