The reason why this or similar orders got rejected by NetSuite
It seems that the customer with this NetSuite "______" internal ID OR this invalid "_____" NetSuite field doesn't belong to the same subsidiary, as a result, our app couldn't sync this order to NetSuite.
Example:
Sales order not created for customer with NS ID - 1000 [Code=INVALID_KEY_OR_REF] Invalid discountItem reference key 1001 for subsidiary 2.
In the above example, this 1001 discountItem doesn't belong to subsidiary 2, as a result, it cannot be applied to its NS ID - 1000 customer.