Incremental Backup Option is not available with VMware backup, after enabling Change Block Tracking (CBT) Option within VMware.
Check the following points regarding the Changed Block Tracking enabled machine:
1) Is the 'enable Changed Block Tracking' option enabled in the VMware Plugin?
2) During the first Full Backup, run with the Enable Changed Block Tracking for VM option selected, the target virtual machine must be powered off.
3) During the subsequent Full, Incremental or Differential backups, the virtual machine can remain on.
4) No snapshots must exist on a virtual machine at the time of enabling CBT on it. For details, refer to http://kb.vmware.com/kb/1033816 .
5) The re-configuration of this parameter will take effect only after the virtual machine goes through a stun/unstun cycle, including power on, resume after suspend, migrate, or snapshot create/delete/revert
