HomePod 2 Siri does not function properly with Apple TV 4K

I have just bought a HomePod and set it up with my Apple TV 4K. I have connected the audio so that it plays the TV audio and I can even give it instructions like “turn the TV volume down by half”. However if I say something like “open BBC iPlayer” or “turn Apple TV on”, then it just says back to me “I can’t find any TV’s to open apps nearby”.

I have set up all the HomeKit stuff on both of them. All the settings are turned on or connected and they are both set to the same HomeKit Room. The Apple TV says “my home” is connected.

The only thing I can think of is the fact that my Apple TV for some reason is not appearing in my Home app. Is there a way that I can get this to appear in the app? All of the research that I am doing seems to tell me that I have done everything already so I don’t know why it is not visible in the home app.