Hello,
and thanks for reaching out to us with this question.
I tried to replicate your setting in our last 8.5 and it seems I got some differences in the fields.
I'd like you to specify the version you are using.
My first advise is to try this additions:

Register: Deliveries
Action: e-mail
Target: e-mail address
Type: Watch Field:Ship Date
Type: In Range Field: ShipDate Parameter1: 2019-01-01 Paramenter 2:2019-31-12

Please let me know if this gave any hint

Best regards,

Giuseppe