In Demio, you are able to track the number of views your Replays get by utilizing your Activity section.
Open the Event you'd like to view the Insights of and navigate to the Activity tab.
From there, scroll to the bottom to see the Replay Summary, as well as the Resource and Messages Summaries.
If you'd like to see specific Registrants/Attendees/No Shows who viewed or did not view the Replay, navigate to your People tab.
From your People tab, you can select the Session you would like to check, and it will show you who did and did not view the Replay by marking them with a Yes or No in the Viewed Replay column.