FTDv HA failover on VMWARE - monitor interface

[Amitabha]

We deployed FTDv on two different esxi hosts and enabled HA and monitored all data interfaces.

Each FTDv is connected to vnic on vmware Dswitches which connects to physical switches.

We found that when the vmnic fails, FW doesn't fail over because vnic on the vswitch is still up and it cause FTDv to flap between active and standby because they can't talk to each other over the failed link. What will we need to do for FTDv to failover when the only vmnic for the FTDv is down but vnic for the FW is still up.

[MHM Cisco World]

VNIC  is down but the VMNIC is UP, 
I dont think this possible here if I am right.
can you more elaborate how VNIC is down but VMNIC is UP, thanks 
MHM