The reservation status for a train is shown online in a format such as 24-4-2021 WL 273 / WL 189. This indicates that earlier the position was a wait list of 273, and now the wait list has shrunk to 189; i.e., if you were to try to book a ticket now, you would get a wait list position higher than 189. A notation such as 24-4-2021 REGRET / WL 215 indicates that earlier no reservations were being accepted even on the wait list, and now the wait list position is at 215.
In other simple words, the word REGRET means now the reservation is not available for the reserved seat in that class for that day in the train for which you are searching for the ticket. That’s why you should now find the option of another train. Once REGRET is marked, then in no case a confirmed or waiting ticket can be available for that train. Neither the booking of confirmed or waiting tickets can be done.————————————————————