I have no idea why it would trigger Norton Security (I don't use Norton, so I'm not familiar with their services and what can trigger them). Can you share the exact security message it triggers?
If Norton Security has to do with your firewall, it's possible that it's blocking the connection to Twitch itself (or the localhost connection that's needed to gain an auth code) and you would have to allow the program access. But I can't help with that either without more information.