What can I do while a campaign is open?
The Live status tab shows the funnel — invited, sent, opened, completed — and lets you send reminders to the people who haven't responded yet.
The system opens scheduled campaigns and closes expired ones on its own, hourly. You do not need to close a campaign by hand, though you can.
Cancel is available only while a campaign is Draft or Scheduled.
Reminders go only to non-respondents. The system knows who has completed without knowing what they said, which is exactly the point of tracking completion separately from content.