View the error codes of the API in the API reference based on the original error code returned by the IoT platform. If an application has encapsulated error codes, you can use the postman to call the same APIs to obtain the original error code and description returned by the IoT platform, and then rectify the fault based on the recommendation.
The NA may encapsulate errors reported by the IoT platform. The original error codes reported by the IoT platform fail to be obtained if the postman is not used.
For details on how to use Postman to call an IoT platform API, see Using Postman to Test IoT Platform APIs.