Proceeding to Registration from Cart changes status to 'checkout_registration' - which Commerce doesn't recognize.

When a user adds a commerce registration to their cart, goes to the cart, and clicks 'Continue' to go to the Registration page, the order is marked from cart to checkout_registration status.

When commerce_order_load is called, it loops through all order statuses defined, including statuses dynamically created from implementing hook_commerce_checkout_page_info(). Thus, the order is set to checkout_registration, however, when commerce_order_load is called, checkout_registration never seems to be in the array of order statuses.

What happens then is if you bail out of the checkout process at any time, like going back to the home page, then going to your cart, your cart says it is empty despite having an active order open.

To get around this quickly, I created a Rule that looked for an updated order, checked if its status was 'Checkout: Registration' and updated it to 'Checkout: Checkout'. Now, a user can exit the checkout process and come back to their cart and start the checkout workflow again with information they already entered. Otherwise, they get locked out and it is rather frustrating/clunky experience.

But the order status is not being picked up on within Drupal Commerce, which is a bug.