Tapes have to assign manually in tape library

Hi Team,

 previously we use to insert tapes in I/O slot of IBM TS3500 Tape Library and perform inventory in netbackup then tapes use to get insert in desired TLD(robot) which was working fine now

 when we insert tapes in tape library we have to assign those tapes to desired TLD(Robot) from tape library console then we have to perform inventory in netbackup which gets complete.

please help for the same.