Troubleshooting OAuth2 Authentication Errors

Last updated: July 4, 2025

When using Formance APIs, you may encounter OAuth2-related authentication errors. Here's how to resolve common issues:

Invalid Request: grant_type missing

If you receive an error like:

{
  error: 'invalid_request',
  error_description: 'grant_type missing'
}

This means you need to specify the grant type in your authentication request. Make sure to include the grant_type parameter in your request.

502 Bad Gateway Error

If you encounter a "502 Bad Gateway" error when fetching OAuth2 tokens, this typically indicates a temporary connectivity issue with the authentication service. Common causes include:

  • The auth service pod is restarting

  • Node scheduling issues in your Kubernetes cluster

  • Temporary network connectivity problems

To troubleshoot:

  1. Verify the auth service is running: 

    kubectl get pods -n your-namespace | grep auth

  2. Check if the auth pod is in "Running" state with normal restart counts

  3. If using cloud providers like GCP, consider using non-preemptible nodes to avoid scheduling interruptions

Additional Resources

For detailed authentication examples and documentation, refer to our Machine-to-Machine Authentication Guide.