After the order is paid in flu (or not checkout is complete if there is no payment required and I ever get that working) I need to do a bunch of processing to set up the product the user has just bought. Only once that is done can I say the order is complete and I thought this would do it

commerce_order_status_update($order, 'completed');

But it doesn't change the order status. They are always left as Pending.

How do I programmatically change an order status from pending to completed?

After the order is paid in full (or not checkout is complete if there is no payment required and I ever get that working) I need to do a bunch of processing to set up the product the user has just bought. Only once that is done can I say the order is complete and I thought this would do it

commerce_order_status_update($order, 'completed');

But it doesn't change the order status. They are always left as Pending.

How do I programmatically change an order status from pending to completed?