There are several things I’d check.

First, check the TV for updates to its own firmware. Make sure it is running the latest from Sony.

Next, make sure CEC is on. If memory serves, this is called BraviaLink, or something like that, in the audio settings on the TV.

Next, reboot the TV and the Sonos by powering them down. The only effective way to do this is by unplugging them from the wall, just using the remote doesn’t do what you need to occur actually happen. Wait at least two minutes before plugging them back in. 

Check the Sonos for updates as well, to ensure you’re running the latest, by looking in the controller. Don’t look only at the various ‘stores’ for updates, you want to check the speakers to ensure they’re up to date.

If none of this changes anything, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Thank you for the reply. I typically check often for updates on all my gear so I was positive I was running the latest on all devices but coincidentally both the TV and the Sonos updated tonight. So far it has worked flawlessly since the updates but I am definitely keeping my fingers crossed.

Bravia firmware released about two months ago has proved a challenge for reliable ARC connectivity for many.

If your TV has optical out, use that while you wait for Sony to fix their firmware.

Oh ok that is about when my issues started, but so far the latest update has been working since installed last night.

Well the issue isn't gone unfortunately. I ended up switching to optical for now and it has been working for 2 days straight now without issue.   One day when I have the time and inclination I will reach out to Sonos support.