TransferClient returns no error message after failed operation

I have been trying to use TransferClient in C++ from the official SDK following the tests in the SDK. But when I run the following code, I don't get a human readable string. Ideas?

TransferClientConfiguration transferConfig;
transferConfig.m_uploadBufferCount = 20;

static const char* ALLOCATION_TAG = "TransferTests";
ClientConfiguration config;    
std::shared_ptr<S3Client> m_s3Client = Aws::MakeShared<S3Client>(ALLOCATION_TAG, config, false);
std::shared_ptr<TransferClient> m_transferClient = Aws::MakeShared<TransferClient>(ALLOCATION_TAG, m_s3Client, transferConfig);
std::string s3path = "akey";
std::shared_ptr<UploadFileRequest> requestPtr = m_transferClient->UploadFile(filepath.string(), "testbucket", s3path.c_str(), "", false, true);
requestPtr->WaitUntilDone();
if (!requestPtr->CompletedSuccessfully())
{
    // requestPtr->GetFailure() retus a blank string here??
}