can't help but recommend updating to SP4, not even sure if 11.5 will run correctly under 2003 SP2 without it.
https://support.ca.com/irj/portal/anonymous/phpdocs?filePath=0/4536/115/4536_115-patchindex.htmlWith a tape library the default Device Group contains all the slots. Often users create their own Device Groups. Make sure all these tapes are in the same Device Group and the job is configured to use that Device Group.
If the Device Window does not correctly show all the tapes then run a Regular Inventory.