Backup Exec does not recognize media and keeps showing Library is offline

I have just replaced my failed library with a new (exact replacement) Quantum SuperLoader 3 Tape Library (single drive/2-8 tape magazines). It is correctly noted in Device Manager (Win Svr 2008 Std R2) and Backup Exec sees it and has installed drivers for it. My problem is that BE keeps placing it OFFLINE and shows "No Media", when in fact there are 16 LTO4 Ultrium tapes in the two magazines.

When I manually set it to ONLINE, and try to run a job (Inventory/Backup/Restore, etc), BE says that there is no media and shuts down the job, and resets the library to OFFLINE.

Any assistance would be very much appreciated.

Ken