The 'Last active' status in your member list updates when a member was last active in the app. For example, when a member:
Logs in to the app.
Completes or views a workout.
Attends a class or makes a booking.
Views or updates a nutrition or meal plan.
Completes feedback or check-ins.
In short, whenever a member interacts with the app or actively uses their account, 'Last active' is updated in the member list.