Each activity type has a Minimum participants and an Auto cancel activity time. If a session has fewer players than the minimum at that many hours before the start, it is cancelled automatically and players get a full refund.
How to set it
Go to Play → Activities → Types and open the type.
Open the Settings tab and click Edit.
Set Minimum participants.
Set Auto cancel activity (0 to 48 hours before the start; 0 turns it off).
Click Save.
You can also change these for one session, when you schedule it or by editing it.
What happens when a session is cancelled
Nettla checks about every 10 minutes, so the session is cancelled within about 10 minutes of the cut-off.
Players get an email and a push notification.
Everyone who paid gets a full refund to their original payment method.
For a course, only the first session is checked. If it is cancelled, the whole course is cancelled.
When players can leave
If the session has at least the minimum, players can leave right up to the start time.
Players can't leave themselves only when the session is already below the minimum and inside the automatic cancellation window.
If a player leaves and the session drops below the minimum inside the window, the session is cancelled within about 10 minutes.
Refunds when players leave
Players who leave are refunded according to your club's activity cancellation rules in Settings → Rules & Limits → Cancellations → Activities. These rules apply to all activity types; you can't set a different policy per type.
Good to know
If you remove a player and the session drops below the minimum inside the window, it will be cancelled. Add another player first if you want it to go ahead.