Buzz bought an Amazon Fire Stick and has an old Yamaha Receiver for it, but it doesn't have HDMI. He's managed to connect it, but he gets no audio. Leo says that most TVs have one HDMI/ARC. That's the Audio Return Channel. He wants to plug the FireStick there. But he also wants to also use the optical connection for sound. That's what Buzz did, but it doesn't work on the Firestick. Everything else is fine. The audio settings may need to be changed. Look at the TV setup. Try using the PCM Audio setting. The FireTV stick may require an unencoded version, which PCM is. The TV will then pass that on to the AV receiver!
Check out his website buzzrhino.com