Regret meaning in irctc: On ixigo

On ixigo, you may see the term ‘REGRET’ when trying to book a train ticket for a busy route. This happens when the IRCTC reservation system can’t accept new booking requests for a train, because it has exceeded the waitlist capacity for a given date. Regret means that no more tickets are being sold. All available berths are sold out, then waiting list became so long that it is impossible that anyone ticketing now will be confirmed. It means that further booking is not allowed! Regret/WL 1 means no booking allowed at any time and not further booking not allowed. IR can change this with Booking not allowed text. But does not know what is the reason when booking in not allowed they are showing this message. Want to know from experts the reason behind this. In the context of IRCTC, "regret" refers to a status that appears when the reservation system cannot accept new booking requests for a train because it has exceeded the waitlist capacity for that train. This means that no booking is allowed at any time, and further booking is not allowed.