Not receiving responses

Hi, I'm new with the Api of DropBox in general. Right now I'm trying to integrate the api on my iOS app. I followed this steps I managed to get it working on Xcode Version 9.2  with Swift 3.2. I have already signIn with my user and created a folder just as the examples says. What I really want to do is to get the user files list, but I'm making the request almost the same as the creatinFolder but I just dont get a response. I would be very happy with any help 

let client = Dropbox.authorizedClient;
client?.files.listFolder(path:"").response 
{ response, error in
    if let response = response 
    {
        print("Response: ",response);
        let data = response.entries;
        for file in data
        {
            print(file.name);
        }
    } 
    else if let error = error 
    {
        print("Error: ",error);
    }
}