# Response Codes

<table><thead><tr><th width="324">Response Code</th><th>Description</th></tr></thead><tbody><tr><td>200</td><td>Success</td></tr><tr><td>400</td><td>Bad Request (Due to missing required fields)</td></tr><tr><td>401</td><td>Unauthorized (Invalid API Key or Invalid Signature)</td></tr><tr><td>408</td><td>Transaction Expired</td></tr><tr><td>409</td><td>Transaction Duplicate</td></tr><tr><td>499</td><td>Transaction is cancelled by Customer</td></tr><tr><td>502</td><td>Bad Gateway (Cannot connect to Service Provider)</td></tr><tr><td>503</td><td>Service Unavailable (Cannot send request to Service Provider)</td></tr><tr><td>504</td><td>Request Timeout</td></tr><tr><td>505</td><td>Authentication Failure (3DS flow or Not Supporter)</td></tr></tbody></table>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.galaxypay.vn/upc/payment-gateway/appendix/response-codes.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.