Create Elliptical Curve Signing Key using TSS/C++ - c++

Question

I need to create an elliptical signing key using the TSS/C++ library.
However when I create it I get a strange error from the TPM simulator:
TPM Error - TPM_RC::: The specified path is invalid.
Here is the method I use to create the signing key. Can someone show me what I am doing incorrectly
DWORD CreateKeyPair(Tpm2 tpm)
{
DWORD retCode = 0;
try
{
//Create a dummy PIN for now
ByteVec userAuth = ByteVec{ 1, 2, 3, 4 };
TPMS_SENSITIVE_CREATE sensCreate(userAuth, vector<BYTE>());
vector<TPMS_PCR_SELECTION> pcrSelectSigning{};
//signing key
TPMS_ECC_PARMS signingKeyParams(TPMT_SYM_DEF_OBJECT(),
TPMS_SCHEME_ECDSA(TPM_ALG_ID::SHA256),
TPM_ECC_CURVE::NIST_P256,
TPMS_NULL_KDF_SCHEME());
//Signing key public template
TPMT_PUBLIC signingKeyTemplate(TPM_ALG_ID::SHA256,
TPMA_OBJECT::sign | // Key attribues
// Not needed, TPMA_OBJECT::encrypt |
TPMA_OBJECT::fixedParent |
TPMA_OBJECT::fixedTPM |
TPMA_OBJECT::sensitiveDataOrigin |
TPMA_OBJECT::userWithAuth,
vector<BYTE>(),
signingKeyParams,
TPMS_ECC_POINT()
);
CreatePrimaryResponse singingPrimary = tpm.CreatePrimary(TPM_RH::OWNER,
sensCreate,
signingKeyTemplate,
vector<BYTE>(),
pcrSelectSigning);
}
catch (exception e)
{
cout << "Exception thrown: " << e.what() << endl;
}
return retCode;
}