Before switchback, you must verify the CallServerConnector component in the primary site as the CallServerConnector attributes handle the call control and the agent control functions on DC1.
Procedure
On the Monitor Service page, click Cluster 1 > Show cluster Messages.
You can see all the PUs in Cluster 1.
From the Filters column, select CallServerConnector PU.
Verify that the HEARTBEAT message for CallServerConnector PU is INTACT.
