Alarm Active but not in the pipeline

We have a site where an alarm was active but the notification was never sent out. This was showing and an active alarm in the alarm table. This had worked in the past for the same alarm. Other sites use the same pipeline and those notifications are being sent. I can see the alarm in the alarm events table and see the details in the alarm event data table. The alarm events data table indicates the alarm was sent to the proper pipeline.

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The pipeline the alarms are being sent to has a script at the start of the pipeline to log into the audit events table when an alarm has entered the pipeline. This is how I know this particular alarm never made it to the pipeline in addition to the client being so kind as to let me know.

Why would an alarm not make it into the pipeline?