What Sonos device is actually linked to the TV and how is it connected? Have you tried using the volume down button on the TV remote?

I don’t know what your phone is showing, but you can always walk over to the Arc and touch the volume controls on the top.

Sometime the Sonos’ start up procedure after an update confuses routers. Power down you router and your Sonos devices. Start up the router, then the Arc and then one by one the rest of your Sonos devices.

If the power down, reboot and power up works you can likely avoid the problem in the future by using your Router’s DHCP page to set static/reserved IP addresses for all your Sonos deices.

Once done you should so the power/reboot/power one more time to lock in the new addresses.