NOW just transmit what Sky show for the live channels and outside the BBC every single channel has adverts on live channels.
This will give you the information on boost which explains the ad free for on demand content.
As others have said its a bit naive to think that boost or any such service is capable of removing ads from live streamed TV as it simply cant.
My advice is just dont watch anything live again - theres no real need to as things appear on catchup very quickly and sometimes simultaneously as the live show enabling you to actually finish watching the show before its finished being broadcast thats to 15 minutes of ads missing.
Are you thinking Boost is making your soundbar not work?
Does it play audio from every other app and/or source just fine?
If you go into the Boost settings and choose stereo instead of 5.1, does this bring the audio back?
If the answer to all three questions is ‘yes’, please tell us the device on which Now is running, the make and model of TV in use, the make and model of soundbar in use, and how the soundbar is connected to the TV - HDMI ARC or eARC, or digital, or what?
This will narrow down the possibilities for the failure that we need to go through.
If the answer to some of the three questions is ‘no’, post the answers and we will go from there.