plus.downloader.createDownload ios热更新多次提示下载失败

plus.downloader.createDownload( appDownloadUrl.value, {force:true}, function(d,status){
if ( status == 200 ) {
console.log("下载wgt成功："+d.filename);
installWgt(d.filename); // 安装wgt包
} else {
console.log("下载wgt失败！");
plus.nativeUI.alert("下载wgt失败！请关闭应用重新启动");
}
plus.nativeUI.closeWaiting();
}).start();
};