Apple TV 4K not connecting to sound bar

Hello

I bought an apple tv 4k recently, great bit of kit but every now and then it seems to knock my sound bar out of action and now it's really messed it up. My sound bar wont turn on when connected to the tv like it used to and all my audio is now coming out of the tv speakers.

Navigating the tv menu makes sound through the tv speakers as I move and highlight options, if I go into the tv settings and select "audio system" it will continue with using the tv speakers to make these sounds. My sound bar doesn't turn on to acknowledge I tried to set it as my audio output anymore (I've had to do this in the past if I paused a show for too long and the sound bar would turn itself off, so a simple turn back on using the action button on my remote would always work).

If I go to my apple tv with tv speakers selected on the tv settings then I will get the apple navigation noises. If I then turn on my audio system for the sound bar through the tv settings I get no noises at all so I'm currently forced to use tv speakers only.

I've had my tv with sound bar set up for about 5 years and no issues, this only started to get more frequent when I got my apple tv. Previously it wouldn't send the sound to the sound bar but the lights would still come on if I used the apple remote for volume control (so I removed the apple remote from doing that) so this is an escalation in issues.

My set up is a Sony tv with HDMI 1 port going to apple tv 4K and HDMI 4 (ARC) port into my sony sound bar

note - without unplugging anything I was able to connect my phone via bluetooth to the sound bar and play music so I know it works in it's sound emitting function

Please help :)