Thanks for posting here in the Google Nest Community.
I know how it feels when something isn’t working as it should. What message are you getting when you try to play music to your speaker group? What steps have you taken to fix the issue?
You can delete and create a new speaker group, then observe if it makes a difference. Check out the steps below on how to delete a speaker group.
Delete an existing group:
Check out this article for more information.
Keep me posted.