# Troubleshooting a Test Case
source: https://developer.mastercard.com/account-to-account-commerce-for-dsp/tutorial/postman-ies-tutorial/step5/index.md

## Troubleshooting a Test Case {#troubleshooting-a-test-case}

If you receive an error for an API, navigate to the Failed tab within the Test Results section. Check the reason for the failure and debug the issue before making a new request.

Common issues that we might encounter:

* Invalid DSP_ID (X-Participant-ID header): To resolve such error, update X-Participant-ID header with valid DSP_ID. ![Invalid DSP ID](https://static.developer.mastercard.com/content/account-to-account-commerce-for-dsp/uploads/ies-invalid-dsp-id.png)
* Invalid Product ID: To resolve such error, update X-Product-ID header with valid PRODUCT_ID. ![Invalid Product ID](https://static.developer.mastercard.com/content/account-to-account-commerce-for-dsp/uploads/ies-invalid-prod-id.png)
* Invalid Signature: check signature. We create a signature for the payload and populate the header. There can be multiple reasons for an invalid signature error:
  * Are the correct key-pairs being used?
  * Is the 'X-JWS-Signature' header sent with the signature?
  * Is the value of the header tampered with or altered? ![Invalid Signature](https://static.developer.mastercard.com/content/account-to-account-commerce-for-dsp/uploads/ies-invalid-signature.png)

In the scenario where Postman can't send your API request due to some network issue, you may receive errors such as:

1. Socket Hang up, where the server closed the connection for some reason. An example of why this may occur is an incorrectly input client certificate or participant identifier preventing the message from reaching the server.   

2. ECONNRESET, where an endpoint may be resetting the connection for some reason. An example of why this may occur is an incorrectly input endpoint URL triggering the reset of the connection.  

A list of common issues that may trigger a range of errors when testing your API on Postman can be found in the [Postman Learning Centre](https://learning.postman.com/docs/sending-requests/troubleshooting-api-requests/). If issues persist, please contact your Mastercard implementation manager for further assistance.