> ## Documentation Index
> Fetch the complete documentation index at: https://docs.golance.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Handling errors

## Authentication Errors

All goLance API endpoints require a valid OAuth 2.0 access token.
If the token is missing, invalid, or expired, the API responds with a `401 Unauthorized` status and a JSON error message:

```json theme={null}
{
  "error": "invalid_token",
  "message": "Invalid token: access token is invalid"
}
```

### Expired Token

If your access token has expired, you must generate a new one.
See [Create Access Token](/api-reference/authentication/create-access-token) for instructions on how to obtain a new token.

### Invalid or Missing Token

If you receive the same error even with a token, verify that:

* The token value is correct and complete.
* The token has not been revoked or replaced.
  If necessary, request a new one using the same authentication process.

### Server Errors (5xx)

If the API returns a `5xx` status code (for example `500 Internal Server Error`), it means that an unexpected error occurred on the goLance servers.\
These errors are usually temporary.

**Recommended handling:**

* Retry the request after a short delay (for example, 5–10 seconds).
* If the error persists, contact [goLance Support](https://golance.com/contact-us) and provide the request details (endpoint, timestamp, and response body if available).