Read again, a warning will be displayed on the ECAM not a continuous audible warning
Watch this video, specially at 5:00 and you will see the warning just sounds once
BUT having said since there was a warning heard on the ATC recording, that means the there was a malfunction on the landing gear, So this means the pilot did not do the manual extension and tried to land on its belly but for some reason did not declare an emergency and the ATC was not aware of it, later on after bumping the aircraft did a go around and did the manual extension that worked, but at that time the engines had given up.
Come to think of it, this does not make any sense, why didn't the pilot lower the gear manually? And even if that didn't work why didn't he declare a mayday at that time and inform the ATC of this issues? Since pilots have no visual clues as to the actual situation of the gear and if they have any doubt they call the ATC to check and then they do a low and slow flyby of the runway for people on the ground to see what the actual situation is and radio back to them the scenario.
None of this happened, what is obvious is for some reason the pilot decided to land wheels up ( has been done successfully in the past ) but just as the plane made contact with tarmac changed his mind and did a go around and this time round they were able to extend the gear