A sales order containing a back-to-back item has been created. However, when you ran the supply plan in Planning Central, the supply for the sales order was not released. Why was the supply not released? 

The supply plan should have been run in Supply Chain Orchestration, not Planning Central. 

Planning Central cannot create back-to-back supply, so the supply cannot be released. 

Only Global Order Promising and Supply Chain Orchestration can be used to release and create new supplies for back-to-back orders. 

The supply must first be created in Global Order Promising and then it can be released from Planning Central.