It is important for all SPS/Access Gateway Agents to use an ACO that was created from the SPSDefaultSettings ACO template. If this template is altered, or deleted, how can it be recovered?
The best way to recover this ACO template is to export it from an environment where it is present and import it where it is needed.
Since Agent Configuration is a granularly exportable object in XPSExplorer, use XPSExplorer to find the SPSDefaultSettings ACO template and add it to the Xcart. Save the XCart to a file and then use the Xcart file to export the ACO template from the system that has it. XPSImport can be used on the receiving system to import the missing object.