Flow trigger failure
A flow trigger failure occurs when an automated email sequence stops starting for new subscribers. The trigger event fires, but the flow does not enrol the subscriber and no email is sent.
Definition
What a flow trigger failure is
A triggered flow is an automated sequence that starts when a subscriber performs an action or meets a condition. A welcome series triggers on subscription. An abandoned cart flow triggers when a cart sits idle for three hours. A re-engagement campaign triggers when activity drops below a threshold.
A flow trigger failure happens when the event fires in the source system, but the subscriber never enters the flow. The action occurred, the condition was met, but the expected email sequence does not start. The inbox stays empty.
Common causes
What causes a flow to stop triggering
Webhook timeout or failure
The source system sends the trigger event via webhook, but the endpoint times out or returns an error. The platform never receives the event, so the flow never starts.
CDP sync lag
The trigger depends on an attribute that syncs from a customer data platform. If the sync runs on a schedule and lags, the subscriber reaches the trigger window before the updated data arrives. The platform evaluates the condition against stale values and does not enrol.
Suppression list collision
The subscriber appears on a suppression list that blocks entry into all flows. The trigger fires, but the platform silently skips the subscriber at the entry gate.
Entry filter logic error
The flow has an entry condition that checks multiple fields. One field is missing or incorrectly formatted, the logic evaluates as false, and no one enters. The flow sits live but idle.
Platform outage or degradation
The sending platform experiences a partial outage that blocks new flow enrolments while leaving campaign sends and existing flow sends unaffected. The symptom is selective, and dashboards show no error.
Flow paused without notice
Someone pauses the flow manually or a scheduled pause rule activates. The platform stops processing new entries, but no alert fires to the broader team.
Why the platform does not catch it
Silent failures leave no trace
The platform reports what it attempted, not what subscribers received. If the webhook never arrives, the platform has no record of the trigger event. If the entry filter blocks a subscriber, the platform logs the block internally but does not surface it as an error. The flow remains marked as active, the dashboard shows green, and no alert fires.
I have worked with a broadcaster that runs a Saturday morning newsletter via a triggered flow. One Saturday, the first hour of the send window passed with no emails arriving in subscriber inboxes. The platform dashboard showed the flow as live and healthy. The trigger event had fired in the content management system, but a webhook timeout meant the ESP never received it. Subscribers saw nothing. The platform had no failed-send logs because, from its perspective, no send was attempted. The symptom was the absence of the expected agent send, not an error event the platform could flag.
How monitoring catches it
Heartbeat checks detect missing sends
Telltide monitors operate in heartbeat mode for flows that should fire at predictable intervals. A test identity triggers the flow, and Telltide waits for the expected email to arrive. If the inbox stays empty beyond the acceptable window, the monitor alerts.
The check is inbox-side. Telltide does not query the platform's API or parse webhook logs. It waits for the email. If the email does not arrive, the alert fires. This catches webhook failures, sync delays, suppression collisions, and entry filter errors that the platform itself cannot see.
For the broadcaster, late arrival in the first 30 minutes of the window is almost always a scheduling or timezone issue, not a genuine breakage. But when the inbox is still empty 45 minutes in, that is the signal. Telltide caught it under two minutes from breakage to alert, and the team had time to trigger a manual batch send as a fallback while debugging the webhook timeout.
FAQ
Common questions about flow trigger failures
- How do you know a flow has stopped triggering?
- The inbox stays empty when it should contain a send. For a welcome flow that normally fires within five minutes of subscription, the absence of that first email is the signal. Platform dashboards often show the flow as active, so inbox-side monitoring is the reliable check.
- Why does the platform not alert when a flow stops triggering?
- The platform reports what it attempted, not what subscribers received. If the trigger event never reaches the platform, or if entry filters quietly block every subscriber, the platform has nothing to report. The flow remains marked as active, and no alert fires.
Related terms
Concepts that travel with flow trigger failures
- Triggered flow: an automated sequence that starts when a subscriber meets a condition.
- Webhook trigger: a method for starting a flow when an external system sends an event.
- Journey step: the individual units that make up a flow. Trigger failures prevent the first step from ever firing.
- Email suppression: lists that block sends, including flow entry, for specific addresses.
- Dynamic content: personalisation logic that can break similarly if data sources fail, though inside a single email rather than at flow entry.
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