Symptom
In the document : HA SSO Deployment Guide for C9800, the "System and Network Fault Handling" matrix is for release 17.2 and is old information for recent active releases.
This behavior (whether you will see switchover or not per specific scenario/condition) for C9800 running 17.5.1 or later is different from what the guide says.
[High Availability SSO Deployment Guide for Cisco Catalyst 9800 Series Wireless Controllers, Cisco IOS XE Bengaluru 17.5]
https://www.cisco.com/c/dam/en/us/td/docs/wireless/controller/9800/17-5/deployment-guide/c9800-ha-sso-deployment-guide-rel-17-5.pdf
[High Availability SSO Deployment Guide for Cisco Catalyst 9800 Series Wireless Controllers, Cisco IOS XE Bengaluru 17.6]
https://www.cisco.com/c/dam/en/us/td/docs/wireless/controller/9800/17-6/deployment-guide/c9800-ha-sso-deployment-guide-rel-17-6.pdf
Conditions
C9800 SSO High Availability, version 17.5.1 or later.
Workaround
There is document bug, no functional impact. You should not expect the result (whether switchover will happen or not) based on the old matrix documentation when you're running 17.5.1 or later releases.
Further Problem Description
Especially, when it comes to RP link down scenario, since 17.5.1, you will not see switchover as long as RMI reachability and GW reachability are maintained. Active box should keep Active status while Standby box will go to Standby-Recovery status.
