Jira Code: MISC-335
One of the reasons why promotion is not working is because the sales order date is the same as the promotion date. The promotion start date must be set a day prior to the transaction date in order to have the promotion applied automatically.
The Suite promotion feature is not compatible with the customer centre. The customers cannot directly open the sales order from the customer centre when the suite promotion is enabled. When you log in to the customer centre and when you list the sales order the result will be shown but when you click to view/edit option then it will show an unexpected error. This suite promotion is one of the reasons why this happens. But if you disable the feature then you will be able to see newly created sales order. But the previously created sales order with the Suite promotion feature will not be able to open even if the feature is turned off.