Calling slot in another thread doesn´t get called - c++

Question

I have a class with a serial interface which transmit some data and emit a MessageReceived signal when some valid data are received:
Serial.c
void Serial::on_serialPort_readData()
{
... Other stuff...
else
{
qDebug() << "Received in serial";
emit MessageReceived(_mReceivedData);
}
}
}
And I have my main window which opens the serial connection and start the message transaction. But I have to receive a lot of data and the transmission will take a while, so I decided to use a QThread for the processing of the received data.
I created a thread and a worker in my mainwindow.cpp (code from here):
mainwindow.cpp
_mThread = new QThread(this);
_mThreadWorker = new Worker();
_mThreadWorker->moveToThread(_mThread);
// Like in the example
connect(_mThread, &QThread::started, _mThreadWorker, &Worker::Progress);
connect(_mThreadWorker, &Worker::Finished, _mThread, &QThread::quit);
connect(_mThreadWorker, &Worker::Finished, _mThreadWorker, &Worker::deleteLater);
connect(_mThread, &QThread::finished, _mThread, &QObject::deleteLater);
connect(_mProtocolInterface, &Serial::MessageReceived, _mThreadWorker, &Worker::UpdateData);
_mThread->start();
// Send the first packet so the receiver will answer
The serial interface will send the data in different packages and I read here that it is a bad idea to use the serial port in a seperate thread, so I decided to use the serial port in the main thread and connect the MessageReceived signal with an UpdateData slot of my worker:
worker.h
class Worker : public QObject
{
Q_OBJECT
...
public slots:
void Progress(void);
void UpdateData(QByteArray Data);
public:
Worker(QObject* parent = nullptr);
~Worker();
...
};
worker.cpp
void Worker::UpdateData(QByteArray Data)
{
qDebug() << "Received in Worker";
_mData = Data;
}
void Worker::Progress(void)
{
while(_mActive)
{
switch(_mState)
{
case STATE_INIT:
{
_mState = STATE_INIT;
// Just a idle to simulate the data transfer during debugging
break;
}
}
}
}
But only the slot on_serialPort_readData gets called after I receive the data from the receiver:
>> Received in serial
So why the slot UpdateData of the class Worker doesn´t get called?