Installation of AdminUI was completed without any errors.
Registering the Admin UI to the Policy Server results in the error:
XPSRegClient siteminder -adminui-setup
[XPSRegClient - XPS Version 12.8.0600.2278]
Log output: /CA/siteminder/log/XPSRegClient.2020-08-04_065427.log
Password:
Confirm password:
Initializing system, please wait...
Validating client name, please wait...
(FATAL) : [sm-xpsxps-04670] Invalid administrator credentials.
(Note: there is no smreg file present in the <SiteMinder-Home>/bin folder)
Release : 12.8.x Policy Server
Component : SMPLC
All objects had not been imported into the policy store, per the documentation.
After importing all objects everything worked as expected and they were able to register.
Ensure all Data Definitions and Objects have been imported into the store (or upgraded) per the upgrade documentation.
Reference: Upgrade Policy Store