Nothing showing under devices on Media Server but CAS shows all devices

Situation:

1.  One CAS a, 3 Media Servers xyz, SSO

2.  BEWS 11d, 7170, SP3, HF 37, installed on all servers, as is the SSO.

3.  One HP Autoloader (SCSI), One Dell Powervault 132T (SAN FC), One ARCvault 24 (SAN FC)

4.  CAS shows ALL media servers xyz and ALL devices connected to servers xyz, both fibre and SCSI

5.  On server z devices tab shows NO other media servers and no tape devices.

6.  Under device manager on server z, the FC ARCvault shows exactly as it does on server x so the OS sees the device.

7.  I can assign jobs from server x to run using the ARCvault with no problem.

8.  Jobs run from server z fail due to Unable to acquire device. 

Questions:

1.  Why do devices show on the CAS 'a' but not from the one server 'z'?

2.  Why do no other servers show under devices on server 'z'? 

This may be just an oversight on my part but it's got me stumped. Thanks for any help.

Richard