Pic 18F2550 MPUSBRead doesn't word

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "stdio.h"
#include <windows.h>
#include <QErrorMessage>
#include <mpusbapi.h>
#include <iostream>
#include "mpusbapi.h"
#include <QMessageBox>
#include "math.h"


using namespace std;

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    LoadDLL();

    PCHAR pVID_PID = "vid_04d8&pid_000c";

    BYTE SendData[64];
    DWORD SendLength = 16;
    PBYTE ReceiveData;
    DWORD ReceiveLength=16;
    UINT SendDelay = 50;
    UINT ReceiveDelay = 50;


    DWORD version = MPUSBGetDLLVersion();
    DWORD count =MPUSBGetDeviceCount(pVID_PID);

    cout << "Version: " << version << endl;
    cout << "Count: " << count << endl;

    SendData[0]=0x3f;
    cout << "Sendung: " << (int)SendData[0] << endl;

    cout << "Aufruf SendReceivePacket: " << SendReceivePacket(SendData, SendLength, ReceiveData, ReceiveLength, SendDelay, ReceiveDelay) << endl;
}

MainWindow::~MainWindow()
{
    delete ui;
}

DWORD MainWindow::SendReceivePacket(PBYTE SendData, DWORD SendLength, PBYTE ReceiveData, DWORD ReceiveLength, UINT SendDelay, UINT ReceiveDelay)
{
    HANDLE myOutPipe;
    HANDLE myInPipe;
    PCHAR pVID_PID = "vid_04d8&pid_000c";
    PCHAR pEP = "\\MCHP_EP1";

    myOutPipe = MPUSBOpen(0,pVID_PID, pEP, MP_WRITE,0);
    myInPipe = MPUSBOpen(0,pVID_PID, pEP, MP_READ,0);

    cout << "MyOutPipe : " << myOutPipe << endl;
    cout << "MyInPipe  : " << myInPipe << endl;

    DWORD SentDataLength;
    DWORD ExpectedReceiveLength;
    UINT Result = 100;

    ExpectedReceiveLength = ReceiveLength;
    if ((myOutPipe != INVALID_HANDLE_VALUE) && (myInPipe != INVALID_HANDLE_VALUE))
    {
        if(MPUSBWrite(myOutPipe,SendData,SendLength, &SentDataLength, SendDelay) != 0)
        {
            if(MPUSBRead(myInPipe, ReceiveData, ExpectedReceiveLength, &ReceiveLength, ReceiveDelay) != 0)
            {
                if(ReceiveLength = ExpectedReceiveLength)
                {
                    Result = 1; //erfolgreich
                }
                else
                {
                    Result = 2; //falsche RückgabeLänge
                }
            }
            else
            {
               CheckInvalidHandle(myOutPipe, myInPipe);
            }
        }
        else
        {
            CheckInvalidHandle(myOutPipe, myInPipe);
        }
    }
    return Result;
}



void MainWindow::CheckInvalidHandle(HANDLE myInPipe, HANDLE myOutPipe)
{
    if(GetLastError() == ERROR_INVALID_HANDLE)
    {
        MPUSBClose(myOutPipe);
        MPUSBClose(myInPipe);
        myOutPipe = myInPipe = INVALID_HANDLE_VALUE;
    }
    else
    {
        cout << "Fehler " << GetLastError()<< endl;
    }
}