Have you checked Device Monitor?
What is the status of the tape drives?
Have you had backup failures recently? Status 84's perhaps?
How old is the media that you have added to the tape library?
Or are they perhaps write protected?
Multiple media errors (bad tapes) will cause drives to be DOWN'ed.
Check Windows Event Viewer logs for device-related errors.
If you do not have bptm log folder on the master and/or media server(s), please create it for further troubleshooting.
Check error file in ...netbackup\db\media folder for errors in the last day or two - this will help to narrow down the problem to faulty media and/or faulty tape drives.
