一键升级android 6.0.1可以运行升级到android 8.0.0不可升级下载后不能安装

mui.plusReady(function() {  
                 var client;  
                    if(mui.os.ios) {  
                        client = 'ios';  
                    }else{  
                        client = 'android';  
                    }   
                var zhcn=localStorage.getItem("lastname");   
//var _config = {url : 'http://www.xxxxx.com/'}   
                 var _config = {url : urlajax};  

                var checkUrl= _config.url + "index.php/Home/Soed/updupd";  

             //自动更新,检验在登陆之前就开始执行-提示功能  

                var checkUrl= _config.url + "index.php/Home/Soed/updupd_auto";  
            plus.runtime.getProperty(plus.runtime.appid,function(inf){  

                var wgtVer = inf.version;  

                $.ajax({  
                    type:"post",  
                    url:checkUrl,  
                    dataType:"json",  
                    //data:"{'method':'checkVersion','checkValue':'mainsoft','Rows':{'version':'"+wgtVer+"'}}",  
                    data:{ver : wgtVer,client:client,zhcn:zhcn},  
                    success:function(data){  
                       // console.log(JSON.stringify(data));  
                          console.log(JSON.stringify(data));  

                        if(data.Success == "false"){  

                            var nav_ok=data.nav;  

                            var zhcnok=localStorage.getItem("lastname");  
                            var xinban=eval("json."+zhcnok+"['faxiang_']"); //发现新版本  
                            var Update_Now=eval("json."+zhcnok+"['Update_up_ok']"); //立即更新  
                            var Next_Time=eval("json."+zhcnok+"['Next_Time']"); //下一次再说  

                             mui.confirm(nav_ok,xinban,[Update_Now,Next_Time],function(e){  
                            // mui.confirm('做了一些体验优化，使用更加顺手。','发现新版本',['立即更新','下次再说'],function(e){  
                                //mui.confirm('内容','标题',['立即更新','下次再说'],function(e){  

                                if(e.index==0){  
                                   // downWgt();  
                                     downWgt(_config.url + data.url); //下载更新版的地址   
                                }else{  
                                    return;  
                                }  

                             })  

                        }else{  
                            return;  
                        }  
                    },  
                    error:function(err){  

                    }  
                });  

            });    

         //end   -提示功能  

            // 下载wgt文件   

              var wgtWaiting = null;  
            function downWgt(wgtUrl) {  
                var zhcnok=localStorage.getItem("lastname");  
                var ks=eval("json."+zhcnok+"['Update_domond']"); //开始下载  
                var kaishi=eval("json."+zhcnok+"['Update_kanshi']");//开始安装  
                var yinyong=eval("json."+zhcnok+"['Update_onfind']");//应用升级失败！  

                var fuwuqi=eval("json."+zhcnok+"['Update_fuwuqi']"); //已连接到服务器  
                var xiazhai=eval("json."+zhcnok+"['Update_ok_domol']");//已下载  
                var xiazai_wancheng=eval("json."+zhcnok+"['Update_ok_yes']");//下载完成！    

                wgtWaiting = plus.nativeUI.showWaiting(ks); //开始下载  
               // var wgtUrl = "http://192.168.101.148:7004/AppUpdateWgt/H54BA566C.wgt";  
                var wgtOption = { filename: "_doc/update/", retry: 1 };  
                var task =   
                plus.downloader.createDownload(wgtUrl, wgtOption, function (download, status) {  
                    if (status == 200) {  
                        wgtWaiting.setTitle(kaishi); //开始安装  
                        installWgt(download.filename);  
                    }else{  
                        mui.alert(yinyong);//应用升级失败！  
                        wgtWaiting.close();  
                    }  
                });   

                task.addEventListener("statechanged", function (download, status) {  
                    switch (download.state) {  
                        case 2:  
                            wgtWaiting.setTitle(fuwuqi);  //已连接到服务器  
                            break;  
                        case 3:  
                            var percent = download.downloadedSize / download.totalSize * 100;  
                            wgtWaiting.setTitle(xiazhai+ parseInt(percent) + "%");  //已下载  
                            break;  
                        case 4:  
                            wgtWaiting.setTitle(xiazai_wancheng);  //下载完成  
                            break;  
                    }  
                });  
                task.start();  
            };  

                    // 更新应用资源    
                 function installWgt(path){  

                            if(localStorage.getItem("lastname")=="cn"){  
                                    var Install_update=eval("json.cn['Install_update']");     
                                    var Update_ok=eval("json.cn['Fail_update']");     
                                    var Fail_update_file=eval("json.cn['Fail_update_file']");     
                             }else{                       
                                    var Install_update=eval("json.en['Install_update']");  
                                    var Update_ok=eval("json.en['Update_ok']");    
                                    var Fail_update_file=eval("json.en['Fail_update_file']");       
                             }  

                      //  plus.nativeUI.showWaiting(Install_update);  

                        plus.nativeUI.showWaiting(Install_update, { padding: '15px',round: '20px',loading:{display: 'inline',interval:"100ms"}});  

                        plus.runtime.install(path,{},function(){  
                            plus.nativeUI.closeWaiting();          
                            plus.nativeUI.alert(Update_ok,function(){  
                                plus.runtime.restart();  
                            });  
                        },function(e){  
                            plus.nativeUI.closeWaiting();          
                            plus.nativeUI.alert(Fail_update_file+"["+e.code+"]："+e.message);  
                        });  

                    }  

});

求解决