It seems that the sales order form that you have entered in our app has an element "_____" that is not checked as "SHOW", as a result, our app couldn't sync this order to NetSuite.
Example:
Sales order not created for customer with NS ID - "____" [Code=INSUFFICIENT_PERMISSION] You do not have permissions to set a value for element Item.rate due to one of the following reasons: 1) The field is read-only; 2) An associated feature is disabled; 3) The field is available either when a record is created or updated, but not in both cases.
In the above example, the sales order form doesn't have this "rate" field under the Items sub-tab checked for "Show", as a result, this order got rejected by NetSuite.