nestedlist autopaging can only pageing once ,pull again no response,can anyone help me?

Code:
Ext.define('ux.plugin.ListPaging', {
    extend: 'Ext.plugin.ListPaging',
    alias: 'plugin.ux-listpaging',
    
    
    loadNextPage: function() {
      console.log('ux-loadNextPage');
      this.fireEvent('loadNextPage');
      
        //Load the next page
        this.setLoading(true);
        this.scrollY = this.getScroller().position.y;
        Ext.getStore('reviewStore').nextPage({ addRecords: true } );
    }
});
Ext.define('MyApp.view.MyBlog', {
    extend: 'Ext.Container',
    requires: [
        
        'Ext.MessageBox',
        'Ext.Container' 
    ],
    xtype : 'myblog',
    config: {
     layout: {
     type: 'fit'
    },
 
      
      items: [
                   {
                          xtype: 'nestedlist',
                          id:'reviewnestedlist',
                          title: '\u7533\u8FF0\u5E73\u53F0',
                          displayField: 'title',
                 
                          listConfig: {
                               limit: 12,
                              disableSelection: true, 
                               plugins: [ { 
                                                             
                                  xclass: 'plugin.ux-listpaging',
                                  loadMoreText: 'Load More Incidents...',
                                  noMoreRecordsText: 'All Incidents Loaded',
                                  autoPaging: true ,
                               } ,
                               {
                                  xclass: 'Ext.plugin.PullRefresh' ,
                               }
                               ]
                          }, 
                
                          store: {
                             type: 'tree',
                             id:'reviewStore',
                              fields: [
                                'title', 'content',
                                {name: 'leaf', defaultValue: true}
                              ],
                              
                              autoLoad: true,
                              root: {
                                  leaf: false
                              },
                              
                              
                              pageSize: 12,
                              clearOnPageLoad: false,
                              proxy: {
                                type: 'jsonp',
                                url: 'http://58.1.1.1/get_goodJoker.aspx',
                                
                                pageParam: 'page',
                                limitParam: 'rpp',
                                extraParams: {
                                    q: 'sencha'
                                },
                                
                                reader: {
                                    type: 'json',
                                    rootProperty: 'Discussions'
                                }
                              }
                           },
                           detailCard: {
                               xtype: 'panel',
                               scrollable: true,
                               styleHtmlContent: true
                            },
                            listeners: {
                               itemtap: function(nestedList, list, index, element, post) {
                                   this.getDetailCard().setHtml(post.get('content'));
                               }
                             }
               }
               ]
         }  //config
    });