Your client did not log in to their Guest Application when making the booking
If your client booked without logging into their Guest Application and did not manually fill in the Pass Number field, no session will be deducted from their pass.
They did not enter the number of their pass
If your client does not use Guest Application and forgets to fill in the Pass Number field when booking, no session will be deducted from their pass.
Booking the wrong service
It may happen that your client booked a service that their pass is not valid for.
Expired pass
If your client pass has expired, even if there is session left, they cannot use it.
Service booked before purchasing pass
If your customer booked the service before purchasing the pass, the sessions will not be deducted from their pass. -in this case, you have to manually assign the pass for the appointment.