error requesting media, TpErrno = Robot operation failed

[jeremylo]

Encounter this problem after replace the tape library (plus its tape drives)

The old Robot and Drives are manually removed in the console. And the new added Robot and Drives were detected.

When attempt to restart the previous failed backup job. It stay at the "Mounting" status for a long time and eventually show "error requesting media, TpErrno = Robot operation failed" message.

Did I missing something after replace the tape library?

[Marianne]

Was Device Management Service restarted after removing robot and drives (necessary to remove EVERYTHING). 
Removing devices will move media to None/standalone.

Running Device Config wizard will re-add robot and tape drives (provided everything seen correctly at OS-level).
The wizard will prompt to restart services and create storage unit. 
If ALL attributes are the same (robot number and drive density), this step is not necessary.

When devices have been added, you need to run Inventory.
Double-check that drives and media have the same density.
Use robtest to test mount/unmount. 

[Amol_Nair]

just to add do check the system on the media server as well.. on windows it would be the event viewer application logs for relevant tld errors at the time of mount