Try this,To make sure your messages are successfully executed, sent and
delivered, Journey Optimizer offers capabilities to monitor the messages
that are currently published and triggered. You can see how your
messages are performing across journeys in real-time from the Executions
list.This Message view shows you Sent, Delivered, Excluded ect..
https://experienceleague.adobe.com/docs/journey-optimizer/using/reporting/message-monitoring.html?lang=en
This (below) is another link that gives you a ...