What cause ZD Smart Redundancy Failover

[andi_achridhan_]

What exacly cause ZD failover.. 
Recenly they swing each other 

2018/12/03  07:57:27High [Smart Redundancy] Peer ZoneDirector[10.253.1.1] connected, system is in active state.
2018/12/02  13:46:07High [Smart Redundancy] Peer ZoneDirector[10.253.1.1] connected, system is in standby state.
2018/12/02  13:46:03High [Smart Redundancy] Peer ZoneDirector[10.253.1.1] connected, system is in active state.

if it said lost connection.. from where?
please correct me.. if ZD A cant connect to ZD B they both will state active right? because they think the other ZD is down..

[satyanarayana_m]

I have ZD 1200 configured in smart redundancy mode. suddenly active ZD gone to stand by mode with out apparant reason. can any body clarify reason for failure and and how to restore to main ZD