Enable Content Audio on All TVs in Combined Vivi Rooms
By default, only one TV plays audio in combined rooms. Here's how to enable sound on all TVs:
When in a combined room you can set the sound to come from all displays by;
Clicking on the Cog Icon on the top right

Selecting Room Settings and ticking the ‘All Display Audio’ tickbox;

For a combined room- You’ll be asked to specify how long you wish the all display audio setting to persist.