Resolution: The alarm means “No Idle/ Backup systems are available to replace a failed Primary system.” You want to make sure no change was made to the total # of systems in the group. Check that the # Systems setting (Path: Main > Setup > Group > Group Config) agrees with the actual number of Systems connected to the Group. Increase this setting to match the number of connected Systems. Check the number of Systems designated for the backup role. Check that the backup Systems are not failed, in the Comm Lost state, or ‘Off’ by checking Status > Group.
If the load actually calls for both units to be online at all times, then you are better off not setting them in a group and have them run individually. On the other hand, if one unit is enough to take care of the load efficiently, then the group option is fine, but you need to figure out why the back system is failing.
If the 2nd unit is assisting primary [both units are running at the same time], then you will get a "Back up not available" message. The reason for this is there is no back up to your back up. Therefore your back up is no longer available because it is being used. It is also possible false system failures are being reported, so check the event log and view the set up for failover events. Failover events in the event log also indicate a System failover has occurred. The backup System has come online due to another online System that either failed or was commanded off. A System Comm Loss is considered to be a System failure if the Comm Loss Failover configuration setting is ‘Yes’ (the default setting). This is under Setup > Group > Group Settings > System Failure Events. If a System failure event occurs, the System in which the alarm occur the system will transition to the failed state, and a backup System is engaged if available. Scroll through the list of possible failure events. The first line indicates whether the event is System-level or Module-level, and the second line indicates the event text.