title: woocommerce_order_status_processing not triggered from customers end
body: <p>I am trying to connect my code to the point where a customer has paid in WooCommerce. Because of different statements that woocommerce_payment_complete does not (always) work, I am now trying to connect to the woocommerce_order_status_processing hook.
  When I create an order as a customer, it shows up as processing in the backend. All e-mails are send (to the shop-owner and to the customer), but my code is not triggered.
  When I edit an order in the backend and set it to processing, the code does get triggered.</p>
  
  <p>I have tried several hooks: woocommerce_payment_complete, woocommerce_order_status_completed in combination with a plugin to automatically set orders to completed, woocommerce_order_status_changed, all featuring the same behavior.</p>
  
  <pre><code>add_action('woocommerce_order_status_changed', 'um_versio_api_create');
  function um_versio_api_create() {
       error_log('payment complete');
  }
  </code></pre>
  
  <p>When I create an order as a customer, it shows up as processing in the backend. All e-mails are send (to the shop-owner and to the customer), but my code is not triggered.
  When I edit an order in the backend and set it to processing, the code does get triggered.</p>