Situation:
When you create a new ASG or modify an existing ASG, not all of the servers in the ACG are available to be added to the ASG.
Resolution:
A client system can be connected to more than one fabric. While the system the Configurator is running on may be able to access all of the servers in its ACG, it is not necessarily the case that the selected client for the ASG can access all of the servers. Only those that can be accessed by the selected server will be available.