Custom Alert is scheduled but is not running

Summary:

Our client have a 3 custom alerts which is a learning expiry notication(45 days prior to expiry notification, 15 days prior and 7 days prior). It is scheduled to run daily. But client said that it wasnt running for some time now. Does this kind of alerts only give output when there the learning item will expired on 45 days/15/7 prior even it is set to scheduled?

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