same issue I upgraded WooCommerce (4.1) and my site crashed…
An error of type E_ERROR was caused in line 21 of the file /var/www/html/wp-content/plugins/delivery-drivers-for-woocommerce/admin/ddwc-functions.php. Error message: Uncaught Error: Call to undefined function wc_get_order() in /var/www/html/wp-content/plugins/delivery-drivers-for-woocommerce/admin/ddwc-functions.php:21
Stack trace:
#0 /var/www/html/wp-includes/class-wp-hook.php(287): ddwc_driver_dashboard_change_statuses(”)
#1 /var/www/html/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array)
#2 /var/www/html/wp-includes/plugin.php(478): WP_Hook->do_action(Array)
#3 /var/www/html/wp-settings.php(562): do_action(‘wp_loaded’)
#4 /var/www/html/wp-config.php(94): require_once(‘/var/www/html/w…’)
#5 /var/www/html/wp-load.php(37): require_once(‘/var/www/html/w…’)
#6 /var/www/html/wp-admin/admin.php(34): require_once(‘/var/www/html/w…’)
#7 /var/www/html/wp-admin/update.php(14): require_once(‘/var/www/html/w…’)
#8 {main}
thrown