The reason why this or similar orders got rejected by NetSuite
It seems that the customer with this NS ID, selected a Shopify shipping method that's not mapped with the appropriate NetSuite shipping method, as a result, our app couldn't sync this order to NetSuite.
Example:
Error: Sales order not created for customer with NS ID - 1170 due to Invalid shipping method.
In this above example, a Shopify customer whose internal ID in NetSuite is 1170, selected a Shopify shipping method that wasn't mapped with the appropriate NetSuite shipping method as a result, this order got rejected by NetSuite.