I would suggest that on the Media Agent that controls this drive, from the MS-DOS prompt
cd \Program Files\Omniback\bin
devbra -dev
and see what is found in the category of 'Tape'. It should contain a serial number and a SCSI path. Just type in the SCSI path that you see from this command into the empty field for the tape library
Your version of DP is very much out of support