Workers Not Receiving Email Notifications

Hi All, Very new to Workfront. Our team is working through our first pilot project. I am a Planner and Project Owner. I receive email notifications every time a task is completed, updates are made, etc., but Worker assignees are not receiving any email notifications of any kind. All Workers have confirmed that their email notifications are set to Instant in My Settings. What are we missing? Thank you! Phillip Phillip Waite Intermountain Health Care, Inc.