Bluetooth pairing with SSP (Secure Simple Pairing) Just Works and no MITM (Man In The Middle)

Hello All,
I have problem with pairing on a Bluetooth Device using SSP (Secure Simple Pairing) Just Works (NoInputNoOutput) and no MITM protection.
From a c++ program I have to discover and pair the bluetooth device.
I can discover the device and I do the pair.

But if I research the device the attribute fAuthenticated on the BLUETOOTH_DEVICE_INFO_STRUCT is FALSE.

This is my code:

BOOL CALLBACK auth_callback_ex_ssp(LPVOID pvParam, PBLUETOOTH_AUTHENTICATION_CALLBACK_PARAMS authParams)
{
	BLUETOOTH_AUTHENTICATE_RESPONSE response = { sizeof(BLUETOOTH_AUTHENTICATE_RESPONSE) };

	response.authMethod = authParams->authenticationMethod; // BLUETOOTH_AUTHENTICATION_METHOD_NUMERIC_COMPARISON
	response.bthAddressRemote = authParams->deviceInfo.Address;
	response.negativeResponse = FALSE;

	// Respond with numerical value for Just Works pairing
	response.numericCompInfo.NumericValue = 1;

	DWORD retVal = BluetoothSendAuthenticationResponseEx(0, &response);

	if (ERROR_SUCCESS != retVal)
	{
		TRACE(_T("BluetoothSendAuthenticationResponseEx() failed! %s"), MsBt7_ErrorDisp(retVal));

		return (FALSE);
	}

	return (TRUE);
}

HBLUETOOTH_AUTHENTICATION_REGISTRATION authCallbackHandleSSP = NULL;

BOOL MsBt7_ExecAuthenticateDeviceEx(PBYTE address)
{
	DWORD dwRes;
	BLUETOOTH_DEVICE_INFO_STRUCT deviceInfo = { sizeof(BLUETOOTH_DEVICE_INFO_STRUCT) };
	HBLUETOOTH_RADIO_FIND hFind;
	HANDLE hRadio;

	hFind = BluetoothFindFirstRadio(&btfrp, &hRadio);

	if (NULL == hFind)
	{
		return (FALSE);
	}

	BLUETOOTH_RADIO_INFO radioInfo = { sizeof(BLUETOOTH_RADIO_INFO) };
	if (ERROR_SUCCESS != BluetoothGetRadioInfo(hRadio, &radioInfo))
	{
		return FALSE;
	}

	CopyMemory(&deviceInfo.Address.rgBytes, address, sizeof(deviceInfo.Address.rgBytes));

	dwRes = BluetoothRegisterForAuthenticationEx(&deviceInfo, &authCallbackHandleSSP, (PFN_AUTHENTICATION_CALLBACK_EX)auth_callback_ex_ssp, hRadio);
	if (ERROR_SUCCESS != dwRes)
	{
		CloseHandle(hRadio);
		BluetoothFindRadioClose(hFind);
		return FALSE;
	}

	deviceInfo.fAuthenticated = 0;
	dwRes = BluetoothAuthenticateDeviceEx(NULL, hRadio, &deviceInfo, NULL, MITMProtectionNotRequired);

	if (ERROR_SUCCESS != dwRes)
	{
		CloseHandle(hRadio);
		BluetoothFindRadioClose(hFind);
		return (FALSE);
	}

	GUID pServiceGuid = SerialPortServiceClass_UUID;
	dwRes = BluetoothSetServiceState(hRadio, &deviceInfo, &pServiceGuid, BLUETOOTH_SERVICE_ENABLE);

	if (ERROR_SUCCESS != dwRes)
	{
		CloseHandle(hRadio);
		BluetoothFindRadioClose(hFind);
		return (FALSE);
	}

	// ... some code to get the com port

	CloseHandle(hRadio);
	BluetoothFindRadioClose(hFind);
	return TRUE;
}

The BluetoothAuthenticatedDeviceEx result is ERROR_SUCCESS and after that the fAuthenticated is TRUE.
I can also get the com port.
But if i try another search the fAuthenticated is FALSE again.

Instead if I do the pairing from the Windows user interface (add bluetooth device ...), I get fAuthenticated = TRUE.

Can someone help me?