Getting time out error for device scan for backup server

Hi Everyone,

                      I'm getting following error while running a "scan for Devices" for Physical Tape Library from Networker NMC.

"Backup devices detection on networker has timed out.Terminating.."

"Detection process for host networker reports nsrmon terminated due to timeout:Errno 946"

what might be the cause ?

The backup environment details :

Networker Version: NetWorker 8.2.4.11.Build.1471 Power Edition/209

Networker server : HP-UX B.11.31 U ia64

Physical Tape Library: Oracle storageTek SL8500