ShipmentSent.CustomerNotification - NOT SENDING?

All of our orders are shipments...

EthanWT wrote:
I don't know what that means.
On the Admin > Order page, are you adding Shipments?

Sorry my apologies, yes every order is being added as a shipment

RE: "... order is being added as a shipment"
I'm still confused about your replies and wondering if that's the issue.

Shipments are a "child" of an order.  One Order can have one or more Shipments, where a Shipment can have one or more order items in it.
On the Admin > Order page, are you adding Shipments using the this page?
https://admin-demo.nopcommerce.com/Admin/Order/AddShipment/1