Email Notification From Linked Module Not Sent When Related Contact Record Email Is Targeted

I have a workflow that is supposed to send a email notification triggered in a linking module edit, and send the email to the related contact record of that linked module. The audit log shows that an email is sent, but no email is received.

If I specify a record owner to be notified instead of the related contact record, the email does go out?

Workflow Condition

When = This rule will be executed whenever the field Participant Status is updated.

Condition =

PS2 Verification Code ISN'T Empty

AND

Participant Status IS Send Assessment Invitation

Instant Action:

Email Notifications

Test Notification

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The Audit Log Shows this:

05:00 PM	Workflow Rule Assessment Invitation Workflow sent an email with subject as Test Notification to 10208
05:00 PM	Workflow Rule Participant Status Workflow sent an email with subject as Participant Status ... to 10208
05:00 PM	Workflow Rule Participant Status Workflow assigned a task named [WS] John Doe Status Changed to Send Assessment Invitation. @10208
05:00 PM	Gray Kinney Updated a Training Participants named 10208