To send a Sales Order from D365 to BC you submit it in D365 which locks the record as Non-Editable. In BC however the Order may need to be rejected either because of data error or human error. Whilst a delete function is visible on the Business Central D365 Sales Order page it performs no function. It should be possible to delete the record at this stage which should revert the D365 status back to Open to allow data correction then re-submission. As it stands just now there is no way to correct an Order that has a data error meaning it remains in limbo between D365 and BC