I'm experiencing issues with webhook delivery in the Cybersource sandbox environment.

I have configured webhook subscriptions with the appropriate products and event types (e.g., customer invoicing and recurring billing), and the subscriptions are marked as ACTIVE. However, I am not receiving any webhook event notifications.

What I tested

• Configured webhook endpoint in my backend (public HTTPS endpoint)

• Tested with and without health check configuration

• Result:

  • Only health check requests are received successfully

  • No actual webhook event notifications are delivered

Additional validation

To isolate the issue, I performed a minimal test using webhook.site:

• Created a webhook subscription pointing to webhook.site

• Did not configure health checks

• Triggered events:

  • Invoice creation

  • Invoice payment

  • Invoice cancellation

• Also used the test webhook endpoint via API and via the Cybersource dashboard

Result

• No requests are received at webhook.site

• This indicates the issue is not related to my backend implementation

What I already verified

• Webhook subscription is ACTIVE

• Correct products and event types are configured

• Tested both via API and through the dashboard

• Waited for propagation after creating/updating the subscription

• Endpoint is publicly accessible and working (confirmed via Postman and webhook.site tests)

Expected behavior

Webhook event notifications (not only health checks) should be delivered to the configured endpoint when events occur or when using the test webhook feature.

Actual behavior

Only health check requests are delivered. No event notifications are received under any tested scenario.

Has anyone experienced similar issues in the sandbox environment?
Is there any known limitation, delay, or additional configuration required for webhook event delivery in sandbox?

Any guidance would be appreciated.