After the upgrade, I can login to admin console using masteradmin user successfully. However, I found two things unexpected.
1, Under "Service and Server Configurations" -> "Strong Authentication" -> "Instance Management" , I could still see the 9.0 version instance there but not the 9.1 ones.
2, Under "Service and Server Configurations" -> "Risk Authentication" -> "Instance Management", I could see the warning message "
Release : 9.1
Component : AuthMinder(Arcot WebFort)