You try to apply an Agent Group for use in Agent Overview regarding testing or other purposes.
No user-defined groups exist which can be applied to agents. Change Group Task cannot be executed.
You created an Agent Group only with Endpoint Server and not User attributes.
You need to create an Agent Group with User Attributes and not Endpoint Server. You need to identify by one of the following:
More attribute choices can be created. See the Administration Guide for your version.
See related article Unable to change agent groups in the enforce console