So, this is no longer a PureDisk or NDMP issue - just NBU with VMware, right?
Can you confirm that you have followed configuration steps as per NetBackup for VMware Administrator's Guide ?
Have you confirmed that VMware credentials are sufficient?
Have a look at these TNs:
What are the minimum permissions needed to properly backup and restore using vStorage api?
http://www.veritas.com/docs/000007351
What are the permissions required for the user configured in NetBackup to logon to vSphere cloud to perform vStorage API based backups and restores?
http://www.veritas.com/docs/000006549
The next thing to look at is port connectivity between the backup host (master?) and VCenter and ESX host(s).
Ensure ports 443 and 902 are open.
- Port 443 to access the vCenter server
- Port 902 between backup server and the ESX/ESXi hosts.
Have a look at this blog:
Nuts and bolts in NetBackup for VMware: Transport methods and TCP ports
https://www-secure.symantec.com/connect/blogs/nuts-and-bolts-netbackup-vmware-transport-methods-and-tcp-ports
and this TN:
VMware Transport Modes: Best practices and troubleshooting
http://www.veritas.com/docs/000094725