Ensure that the Secondary (HA) hub has been updated so that the probe versions all match with the latest UIM version 20.3.3.
HA probe v1.47 works properly in 20.3.x/20.3.3. That said, customers should update their Secondary (HA) Hub to make sure it contains the same exact patches/probe versions, especially when it comes to the hub, robot (controller), nas and alarm_enrichment.
nas should be 9.32-HF1 or higher.
Failover and Failback work as expected and no significant number of alarms should be left in the Secondary (HA) hub queues upon failback to the Primary.
Please also refer to the HA guide. Its a bit dated but still mostly relevant and useful as a guide.