Your handler is up, your URL is registered, but expected events aren't arriving. The webhook isn't failing — the source isn't sending it. Diagnosis is harder than failure modes because there's no error message; you're debugging the absence of something.
Root Causes
1. Event type isn't in your subscription
Most providers let you choose which event types each endpoint receives. You configured the endpoint for charge.succeeded only and now you wonder why customer.subscription.created isn't arriving. Check the provider's dashboard for the subscription list. Stripe shows it under "Endpoints" → click endpoint → "Events to send."
2. Endpoint is disabled or paused
Some providers auto-disable endpoints after consecutive failures. Stripe will disable an endpoint after about a week of nothing but failures. GitHub auto-disables on rapid failure clusters. Check the endpoint's status — disabled endpoints stop receiving anything until manually re-enabled.
3. Filter or scope mismatch
You enabled the event but scoped it to specific resources you don't have. GitHub: organization webhook vs repository webhook — events from one don't trigger the other. Shopify: API scope must include the event's resource. Slack: event subscriptions require the right OAuth scopes (messages.channels for message events).
4. The event isn't actually firing on the source
You expected order.created but the user paused checkout before completing. The event you're waiting for never fires because the underlying business action didn't complete. Check the provider's dashboard for the actual event log — if it's not there, the source-side action didn't happen.
5. Wrong environment
You're testing in the live mode dashboard but your webhook is registered in test mode (or vice versa). Stripe has separate test/live modes; events fire in their respective modes only. GitHub's "Send test webhook" button uses the same secret/URL as real events but only fires from the dashboard.
Diagnostic Sequence
- Check the source's webhook delivery log first. Stripe Dashboard → Developers → Webhooks → click endpoint → "Recent Deliveries" tab. GitHub: repository → Settings → Webhooks → click hook → "Recent Deliveries". Shopify: Admin → Settings → Notifications → scroll to Webhooks. If no deliveries are logged, the source didn't try to deliver.
- If deliveries are logged but not arriving: the issue is between the source and your handler — DNS, network, TLS, firewall. Use the responses shown in the dashboard to debug.
- If no deliveries logged but you expected events: verify (a) the subscription includes that event type, (b) the underlying action actually happened, (c) you're looking at the right environment (test vs live).
- If everything looks right but events don't fire: contact the provider. Sometimes there's a backend issue you can't see.
Test the Pipeline Without a Real Event
Most providers have a "Send test webhook" button on each endpoint config page:
- Stripe: Dashboard → Developers → Webhooks → endpoint → "Send test webhook" — picks an event type, fires a real signed test payload.
- GitHub: repository → Settings → Webhooks → click hook → "Recent Deliveries" → click any past delivery → "Redeliver."
- Shopify: Admin → Settings → Notifications → scroll to Webhooks → click → "Send test notification."
- Slack: app config → Event Subscriptions → "Verify URL" sends a verification challenge; can't easily test other events.
Use these to confirm the pipeline works. If test events arrive but real ones don't, the difference is the trigger: the real-world action isn't producing the event.
How to Use WebhookWhisper for This
Point the source at a WebhookWhisper inspect URL temporarily. Trigger the action that should fire the event. If WebhookWhisper captures it, the source is firing — the issue is downstream of WebhookWhisper. If it doesn't, the source isn't firing the event you think it should be.
Frequently Asked Questions
How do I tell if my webhook endpoint is auto-disabled by Stripe?
Stripe shows a banner on the endpoint config page when auto-disabled. The signing-secret stays valid. Re-enable from the same page once your handler is fixed.
Why do some Shopify events not fire even though I'm subscribed?
Shopify scopes events to API permissions. If your app has read scope but the event requires write, it won't fire. Check Apps → your app → Configuration → API access scopes.
Can I subscribe to all events from a provider?
Some allow it (Stripe's '*' subscription), most don't. Subscribing to everything increases attack surface and your handler must validate every type. Subscribe narrowly to what you actually use.