We have created a Journey that sends an email when a new subscriber is added to a data extension. We then fire the event from the REST API. This all works fine except when the new Subscriber does not already exist in All Subscribers.
If the Subscriber exists in All Subscribers the subscriber enters the Journey and the email is sent.
If the Subscriber does not exist in All Subscribers the subscriber enters the Journey and looks like everything runs through except the email is never sent.
My initial thought was to add the Subscriber to All Subscribers, but I don't see a REST Route to add a Subscriber. This seems like it would be a very common use case. What am I missing?