Playing sound on tv via smartview

When I use smartthings to connect my Samsung s8 to my samsung tv, it only plays the sound through the tv for certain apps, like YouTube. How do I get it to play the sound for other apps, particularly Zoom?

I have an S9 and that works fine - in fact I cast Zoom to the TV only last night.

I think only 1 App at a time can cast Audio - for example, if you are in a Zoom call, you cant get Youtube sound on the TV as Zoom seems to have control.

I appreciate thats the opposite of what you are seeing but it may give you a clue.

I have the same problem even though i only have one app on.