Duplicate Job Failing - E000810D

Hi,

I am experiencing problems with my duplicate job on Backup Exec 2014. I am a new user for Backup Exec 2014 as I used to use Backup Exec 2010 a long time ago.

My Media Tape is suppose to be appendable until the 25th of October (6 more days - Appendable Until: 10/25/2015 7:36:11 PM, however it is saying:

"Append operations cannot be performed on this storage media.

Drive and media mount requested: 10/19/2015 8:08:24 PM
Media mount failed.
Physical Volume Library Media not found."

What could be the problem?

Thanks.