Hi there,
Javay here - from Calendly’s Developer Support team. Thanks for sharing the details of your setup—sounds like you’ve got a solid flow in place, and I can definitely help clarify next steps.
Troubleshooting Calendly Webhook Failures
Since you’re seeing intermittent failures even after verifying your setup, here are some focused recommendations:
1. Check Endpoint Response & Performance
Calendly requires your webhook endpoint to respond with a 2xx status code within 10 seconds. Anything slower—including redirects, timeouts, or 4xx/5xx errors—will cause a retry. If no successful response is received after 24 hours, the webhook is disabled.
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Use Postman or a test script to POST a sample Calendly payload to your endpoint and verify that it returns a 200 OK quickly and reliably.
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If your webhook hits Shopify or Zapier first, be sure that service responds before processing the payload.
2. Review Zapier-Specific Pitfalls
Zapier acts as the webhook subscriber in many integrations, so failures here often trace back to scope, token, or version mismatches.
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Make sure your Zap is using the correct version (Zapier v2) and that your Calendly connection uses OAuth, not an old API key.
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Check the Zap history for failed or skipped jobs—these often include helpful error messages.
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Confirm your trigger is scoped correctly. For example, org-level webhooks are best if you’re scheduling across multiple users or event types.
3. Scope and Redundancy Checks
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Confirm that you’re using an organization-scoped webhook or Zap if you want to receive events for all bookings across the org.
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Check for any duplicate webhook subscriptions pointing to the same endpoint—these can result in missed or conflicting deliveries.
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Use the /webhook_subscriptions API to inspect webhook status and see any retry or disabled flags.
4. Consider Webhook Delivery Limits
Calendly automatically retries delivery up to 25 times with exponential backoff. If the endpoint remains unresponsive (or slow) after those retries, the hook will be disabled. There’s no manual resend option, so be sure your handler is designed to process idempotently and log failures.
If you continue to experience issues after validating these areas, feel free to contact Calendly Developer Support at support@calendly.com with your webhook endpoint URL —it can help dig deeper into delivery logs and behavior.
