Powervault 128T with Arcserve 2000

Trying to get Arcserve 2000 to work with a PV 128T I'm using. I've installed Arcserve 2000 with all the patches. I've configured the 128T device and I can get an inventory of all tapes in the library slots within Arcserve. But every tape I have in the library is marked as 'Unreadable Tape' by Arcserve.

Anyone got any ideas why I'm seeing this? Do I need to install the Arcserve Tape Library option (doesn't seem necessary given I can see the Library perfectly.

Any help much appreciated.