Backup Exec 2010 (R1, R2 and R3), 2012, and 2014 Agent for VMware Virtual Infrastructure integrates with ESX and vSphere vStorage API's for backup and restore operations. If the ESX / vSphere host is not licensed for the vStorage API's then backup and restore operations will not be possible with Backup Exec and the Agent for VMware Virtual Infrastructure.
To check to very the ESX / vShphere host is licensed, check the following areas.
In ESX(i) 3.5 go to Configuration - Licensed Features. The license for "VMware Consolidated Backup" provides access to the vStorage API's (Figure 1).
In ESX(i) / vSphere 4.x, or 5.x, go to Configuration - Licensed Features to verify that "vStorage APIs" are listed.
If the ESX(i) / vShphere host is not licensed for these options please contact VMware to obtain the vStorage APIs license