Cause

The Alert Generation was set up with "Print a report of alerts to be generated instead of generating the alerts" checked off, so the alert report is being saved to My Saved Reports, but no actual alerts (HUB or email) are sending.

You can verify this by:

Navigating to the Scheduler Queue program (System Administration>Scheduler Administration>Scheduler Queue).
Double click on the job in question.
If there is a third section called Output and the output is set to "Save as spalerts[xxx].txt", then the alerts are saving to a report in My Saved Reports instead of sending the actual reports.

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