PureEngage On-Premises

cfgFolder = service.retrieveObject(CfgFolder.class,
                                new CfgFolderQuery(folderName));
When I try to query first time,I am able to get Objects under a folder. But it is throwing NullPointer Exception for every subsequent request. Is it because of Cache? Am I need to use 
retrieveMultipleObjects.
                

Hello,

This is example for confservice usage for all agent group. It may be help,

 public List<CfgAgentGroup> GetAllAgentGroupList()
        {
            try
            {
                var query = new CfgAgentGroupQuery(confService)
                {
                    State = CfgObjectState.CFGEnabled,
                };

                return confService.RetrieveMultipleObjects<CfgAgentGroup>(query).ToList();
            }
            catch (Exception ex)
            {

                throw ex;
            }
        }