Using unreal online subsystem to connect with steam and game sparks

I’m having trouble authenticating my game on game sparks, I am using Unreal’s online subsystem to get an auth token from steam, but I need to convert it from FString to Hex for game sparks to accept it. Here’s what I have so far:

FString USteamHelper::GetSessionTicket()
IOnlineSubsystem* OnlineInterface;
OnlineInterface = IOnlineSubsystem::Get();
FString SessionTicket = OnlineInterface->GetIdentityInterface()->GetAuthToken(0);
int TicketLength = SessionTicket.GetAllocatedSize();
FString HexSessionTicket = SessionTicket.FromHexBlob(*SessionTicket, TicketLength);
return HexSessionTicket;

Error C2664 ‘FString FString::FromHexBlob(const uint8 *,const uint32)’: cannot convert argument 1 from ‘const TCHAR *’ to ‘const uint8 *’

Any help would really be apreciated

If you look at engine source code it is already a Hex String, so just send it to game sparks.