HA setup configured. On one of the nodes, we see that heartbeat not found on interface 0/1.
On one of the nodes, when the command "show HA node" is executed, we see the following:
  Interfaces on which heartbeats are not seen : 0/1
On the other node, we see the following:
 Interfaces on which heartbeats are not seen : None

Problem Cause

Critical Interface 0/1 on Secondary node was disabled which is causing HA heart beats to not transmit or receive.
exec: show HA node
1)      Node ID:      0
        IP:   10.10.10.1
        Node State: UP
        Master State: Primary
        Fail-Safe Mode: ON
        INC State: DISABLED
        Sync State: ENABLED
        Propagation: ENABLED
        Enabled Interfaces : 0/1 0/2 LA/7
        Disabled Interfaces : None
        HA MON ON Interfaces : 0/1 0/2 LA/7
        HA HEARTBEAT OFF Interfaces : None
        Interfaces on which heartbeats are not seen : 0/1
        Interfaces causing Partial Failure: None
        SSL Card Status: NOT PRESENT
        Hello Interval: 200 msecs
        Dead Interval: 3 secs
        Node in this Master State for: 0:0:1:27 (days:hrs:min:sec)
2)      Node ID:      1
        IP:   10.10.10.2
        Node State: UP
        Master State: Secondary
        Fail-Safe Mode: OFF
        INC State: DISABLED
        Sync State: SUCCESS
        Propagation: ENABLED
        Enabled Interfaces : 0/2 LA/7
        Disabled Interfaces : 0/1
        HA MON ON Interfaces : 0/1 0/2 LA/7
        HA HEARTBEAT OFF Interfaces : None
        Interfaces on which heartbeats are not seen : None
        Interfaces causing Partial Failure: None
        SSL Card Status: NOT PRESENT
 Local node information:
        Critical Interfaces: 0/1 0/2 LA/7