The lighthouse library can't make an appointment, the quota is full or the system crashes. According to relevant public information, the first case is that the reservation quota is full. The number of places reserved in the library every day is limited. If the reservation is full, there is no seat. The second possibility is that the library reservation system has collapsed and it is generally impossible to make reservations. So it is also possible that the library can't make an appointment and the reservation quota is full.