If not enough players join a match or activity by the club's deadline, it is cancelled automatically. You get a push notification, an email and a full refund to your original payment method.
Which bookings this applies to
Public matches.
Private matches where players pay their part. A private match paid in full is never cancelled automatically.
Activities with a minimum number of players.
A booking that is full is never cancelled automatically.
When it happens
Each club sets its own deadlines. For example, a match may be cancelled 2 hours before the start if it has only 3 players. While a session is short of players, its page shows a countdown such as "Match auto cancels in 1h 20m".
What you get back
The money goes back to how you paid: card reservations are released, card payments are refunded and wallet payments go back to the wallet.
This happens even if the club normally refunds to a club wallet.
If your card had already been charged (because you paid more than 6 days before), the technology fee isn't refunded.
Courses
If the first session of a course is cancelled automatically, the whole course is cancelled.
Good to know
Invite friends to fill your match or activity in time. See "How do I invite friends to my booking?".
If you leave late and the session drops below its minimum, it may be cancelled for everyone.