ARC will only accept HDMI-ARC or HDMI-eARC connections.

Thanks, the problem is that I saw every time I Select the Tv input where my Arc is attached. Before I could also see the type of input ie Dolby 2, 5.1 etc, now I only see that it is PCM even tough I change the input type. Although it decodes the sound. My input setup is normally Passtrough. Regards 

What is being passed through? You may need to change the settings on those audio/video generating devices, too. They may have been changed to PCM only, for some reason. 

I've checked multiple times and both the cable box and the Fire Stick are set up fine.  It all started when I changed the network, and since then the failure began

Seems like you’ve already decided what the answer is. Can we assume that when you changed the network (whatever that means) that you’ve subsequently rebooted every device? 

I’d recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

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 phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

I will do. Thanks Bruce