When in the HA Cloud Administrative Console and creating a new terminal session the Session Server(s) may have difficulty contacting the Management and Security Server (MSS). This could be due to a network issue or a configuration change which causes a communication issue between the Session Server(s) and MSS.

The administrator can access the initial screen to add the session name, but when attempting to launch the session a screen with the message “Unable to authenticate session.” is displayed instead.

Full article: https://portal.microfocus.com/s/article/KM000013668