Short answer
HubSpot's KB: event triggers only enroll for events after the workflow is turned on. Extra filters are checked only at the moment the event happens. The record must exist before the event. You can't test enrollment with event triggers.
1. In HubSpot
The relevant screen in my demo portal.
2. Worth knowing
For records already past the event, use filter-based triggers instead.
3. Related
Date-based triggers and custom events.