How to Upload a Image with POST to Amason S3 in Qt5/c++ ??

Hello, I'm very new at qt, but I need to upload an image to a Amazon S3 server, but I keep getting this error:

Code:

Failure "Error downloading https://bucket_name.s3.amazonaws.com/ - server replied: Forbidden"

I check all the credencialas and keys and they are working fine because I was able to upload the image with curl comands. The problem was when I tried to implemt the code on qt5.

So this it's the code I'm ussing:

Code:

QEventLoop eventLoop;
    QNetworkAccessManager mgr;
    QObject::connect(&mgr, SIGNAL(finished(QNetworkReply*)), &eventLoop, SLOT(quit()));
 
    QHttpMultiPart *multiPart = new QHttpMultiPart(QHttpMultiPart::FormDataType);
 
    QHttpPart textPart;
    textPart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"key\""));
    textPart.setBody("c_test/Pantallazo-10.jpg");
 
    QHttpPart textPart1;
    textPart1.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"AWSAccessKeyId\""));
    textPart1.setBody("myAccessKeyId");
 
    QHttpPart textPart2;
    textPart2.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"Policy\""));
    textPart2.setBody("myPolicy");
 
    QHttpPart textPart3;
    textPart3.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"Signature\""));
    textPart3.setBody("mySignature");
 
    QHttpPart imagePart;
    imagePart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("image/jpeg"));
    imagePart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"file\""));
    QFile *file = new QFile(QDir::homePath() + "Pantallazo-10.jpg");
    file->open(QIODevice::ReadOnly);
    imagePart.setBodyDevice(file);
    file->setParent(multiPart); // we cannot delete the file now, so delete it with the multiPart
 
    multiPart->append(textPart);
    multiPart->append(textPart1);
    multiPart->append(textPart2);
    multiPart->append(textPart3);
    multiPart->append(imagePart);
 
    QUrl url = QUrl(QString("https://bucket_name.s3.amazonaws.com/"));
 
    QNetworkRequest request(url);
       QNetworkReply *reply = mgr.post(request, multiPart);  // POST
    eventLoop.exec(); // blocks stack until "finished()" has been called
 
    if (reply->error() == QNetworkReply::NoError) {
        qDebug() << "Success";
    } else {
        //failure
        qDebug() << "Failure" <<reply->errorString();
        multiPart->setParent(reply);
        delete reply;
    }

I really don't know what to do next, I'm pretty stuck on this one.