Check for App updates and see if that perhaps fixes it.

I am having the same issue on Windows 11. Updated the controller and the problem is still persisting. Sometimes I can control some speakers’ individual volumes and some I can’t.

Was not happening yesterday evening.

See this link..

There was another App update today, so I wasn’t too sure if the issue might have been resolved, but if not, then hopefully the next update will resolve the issue for you.

Apparently a known issue and they are working on it.

If you follow the link that @Ken_Griffiths posted, you’ll see the response from Sonos. 

Thank you for the updates and direction!

Same thing on Win10.

Windows Controller - Independent Volume Not Working?

Have you read the thread? 
 

Is the increased font size significant?

So Sonos support escalation team says this about this HUGE mess the new update made, basically… maybe by YEAR END!  Really.  You majorly break a MAIN FUNCTION of the PC controller that many thousands of loyal/paying customer use daily/hourly and it’s JUST NOT IMPORTANT enough to fix before the end of the year?   Really?