Events will not work with DataSets that are logged via the Mirror service. In order for the Events service to operate properly, tags must be logged in real time. The Mirror service does not operate in real time.
When the Mirror runs, it takes time based snapshots of other Canary Historian's DataSets. The new data that has been written since the previous snapshot is then transferred into the mirrored DataSet. Events requires a constant scanning of new data, and therefore is not able to handle an absence of updates during the snapshot.
To overcome this, we recommend you dual log the data necessary for Events rather than mirror it. Dual logging consists of configuring a Sender to push data in real time to multiple Canary Historians. This can commonly be achieved by configuring the Data Collector field that targets the historian with multiple historians, separated with a comma and space. For instance configuring the historian field with CanaryHistorian1, CanaryHistorian2 would push data to both historians.