WMI SoftwareLicensingProduct class doesn't show Partial Product Key for MS Office on some systems ( Windows 10)

Question

Using WMI SoftwareLicensingProduct class I am fetching Partial Product Key / License Key for Microsoft Product. Its compatible with Windows Vista and above. But still I am not able to retrieve the Key for MS Office on few Windows10 system, for rest of the systems, its working as expected.

Code :

int _tmain(int argc, _TCHAR* argv[]) {

 HRESULT hres;

// Initialize COM.
hres =  CoInitializeEx(0, COINIT_MULTITHREADED); 
if (FAILED(hres))
{
    cout << "Failed to initialize COM library. " 
        << "Error code = 0x" 
        << hex << hres << endl;
    return 1;              // Program has failed.
}

// Initialize 
hres =  CoInitializeSecurity(
    NULL,     
    -1,      // COM negotiates service                  
    NULL,    // Authentication services
    NULL,    // Reserved
    RPC_C_AUTHN_LEVEL_DEFAULT,    // authentication
    RPC_C_IMP_LEVEL_IMPERSONATE,  // Impersonation
    NULL,             // Authentication info 
    EOAC_NONE,        // Additional capabilities
    NULL              // Reserved
    );


if (FAILED(hres))
{
    cout << "Failed to initialize security. " 
        << "Error code = 0x" 
        << hex << hres << endl;
    CoUninitialize();
    return 1;          // Program has failed.
}

// Obtain the initial locator to Windows Management
// on a particular host computer.
IWbemLocator *pLoc = 0;

hres = CoCreateInstance(
    CLSID_WbemLocator,             
    0, 
    CLSCTX_INPROC_SERVER, 
    IID_IWbemLocator, (LPVOID *) &pLoc);

if (FAILED(hres))
{
    cout << "Failed to create IWbemLocator object. "
        << "Error code = 0x"
        << hex << hres << endl;
    CoUninitialize();
    return 1;       // Program has failed.
}

IWbemServices *pSvc = 0;

// Connect to the root\cimv2 namespace with the
// current user and obtain pointer pSvc
// to make IWbemServices calls.

hres = pLoc->ConnectServer(

    _bstr_t(L"ROOT\\CIMV2"), // WMI namespace
    NULL,                    // User name
    NULL,                    // User password
    0,                       // Locale
    NULL,                    // Security flags                 
    0,                       // Authority       
    0,                       // Context object
    &pSvc                    // IWbemServices proxy
    );                              

if (FAILED(hres))
{
    cout << "Could not connect. Error code = 0x" 
        << hex << hres << endl;
    pLoc->Release();     
    CoUninitialize();
    return 1;                // Program has failed.
}

cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;

// Set the IWbemServices proxy so that impersonation
// of the user (client) occurs.
hres = CoSetProxyBlanket(

   pSvc,                         // the proxy to set
   RPC_C_AUTHN_WINNT,            // authentication service
   RPC_C_AUTHZ_NONE,             // authorization service
   NULL,                         // Server principal name
   RPC_C_AUTHN_LEVEL_CALL,       // authentication level
   RPC_C_IMP_LEVEL_IMPERSONATE,  // impersonation level
   NULL,                         // client identity 
   EOAC_NONE                     // proxy capabilities     
);

if (FAILED(hres))
{
    cout << "Could not set proxy blanket. Error code = 0x" 
         << hex << hres << endl;
    pSvc->Release();
    pLoc->Release();     
    CoUninitialize();
    return 1;               // Program has failed.
}


// Use the IWbemServices pointer to make requests of WMI. 
// Make requests here:

// For example, query for all the running processes
IEnumWbemClassObject* pEnumerator = NULL;

 hres = pSvc->ExecQuery(
    bstr_t("WQL"), 
    bstr_t("SELECT * FROM SoftwareLicensingProduct"),
    WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, 
    NULL,
    &pEnumerator);


if (FAILED(hres))
{
    cout << "Query for processes failed. "
         << "Error code = 0x" 
         << hex << hres << endl;
    pSvc->Release();
    pLoc->Release();     
    CoUninitialize();
    return 1;               // Program has failed.
}
else
{ 
    IWbemClassObject *pclsObj;
    ULONG uReturn = 0;

    while (pEnumerator)
    {
        hres = pEnumerator->Next(WBEM_INFINITE, 1, 
            &pclsObj, &uReturn);

        if(0 == uReturn)
        {
            break;
        }

        VARIANT vtProp;

        // Get the value of the Name property
        hres = pclsObj->Get(L"Name", 0, &vtProp, 0, 0);
        wcout << "Process Name : " << vtProp.bstrVal << " ";
        VariantClear(&vtProp);

         VARIANT vtProp1;

        // Get the value of the PartialProductKey property
        hres = pclsObj->Get(L"PartialProductKey", 0, &vtProp1, 0, 0);
        if (VT_NULL != vtProp1.vt)
            wcout << ": " << vtProp1.bstrVal << endl;
        else
            wcout<<endl;
        VariantClear(&vtProp1);
    }

}
getch();
// Cleanup
// ========

pSvc->Release();
pLoc->Release();     
CoUninitialize();

return 0;   // Program successfully completed.

}