> Common questions and troubleshooting tips ## 1. I'm getting an "Unauthorized" error This usually means you are posting an incorrect or misspelled API key. Double-check that your key is correct and that it is formatted properly in the `Authorization` header. **Example of a failed auth response:** ```json title="401 Unauthorized response" { "error": "werkzeug.exceptions.Unauthorized", "message": "The server could not verify that you are authorized to access the URL requested." } ``` > [!TIP] > Make sure you include the trailing colon after your API key when using Basic Auth (e.g., `YOUR_API_KEY:`). The colon separates the username from the empty password. ## 2. I'm getting an "Unsupported payment method" error Each payment method must be **activated on your account** before it can be used. If you attempt to use an inactive method, the API returns a `400 Bad Request`: ```json title="400 Bad Request response" { "error": "werkzeug.exceptions.BadRequest", "message": "The requested payment method is not active for this merchant." } ``` > [!NOTE] > Contact your Cost+ account manager or enable the payment method in the admin portal under **Settings > Payment Methods**. ## 3. Which test card numbers can I use? See the [Testing Your Integration](/docs/getting-started/testing) page for a full list of test card numbers, including cards that simulate successful and failed transactions. ## 4. How are webhook retries handled? If your webhook endpoint does not respond with a `2xx` status code, Cost+ will retry delivery: - **Up to 10 retries**, spaced **2 minutes apart**. - The **first attempt** times out after **4 seconds**. - **Subsequent retries** time out after **10 seconds**. > [!WARNING] > If all 10 retries fail, the webhook event is marked as failed and will not be retried again. Make sure your endpoint responds quickly and returns a `200` status code. For full details on webhook configuration and payload formats, see the [Webhooks](/docs/guides/webhooks) guide.