Why can’t I reschedule my child’s appointment? You may have exceeded the number of rescheduled appointments or missed your appointment beyond the valid period. Related articles Why can’t I make two appointments for my child? My child is in primary /secondary school. Why can’t I book appointment at Student Dental Centre? What will happen if I cancel my appointment? I am trying to book an appointment, but I cannot find any availability. What should I do? Why are the dates not available for my selection?