What are the correct Filters and Recipient Expressions needed in order to create a Recommended Alert

Summary:

I am attempting to make a custom learning alert using Alerts Composer that notifies a learner when they have been recommended training. When the alert is ran there are no alerts being generated. When I check the alert log it says the recipient expression is evaluated as Null.

Content (please ensure you mask any confidential information):

Recipient Expression Val is evaluted as Null for assignmentRecordId=3###############3

Learning Alert Resource: learningRecommendations

Communication Method Worklist: ${AlertUtils.person(learningRecommendations.assignedToId).UserName}

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Code Snippet (add any code snippets that support your topic, if applicable):