The reason why this or similar orders got rejected by NetSuite
It seems that the customer with this NetSuite "______" internal ID is not mapped with the correct class ID, as a result, our app couldn't sync this order to NetSuite.
Example:
Error: Sales order not created for customer with NS ID - 246429 [Code=INVALID_KEY_OR_REF] Invalid class reference key 32.
In the above example, this 246429 NetSuite internal ID customer is not mapped with the correct class ID, as a result, this order got rejected by NetSuite.