@erik If you haven't already, please be sure to use the Send feedback option in the Stadia app to report this directly to the developers. Doing so will help them to investigate the problem. Thanks!
In party it Shows a question Mark and says "no mic". No one can hear me. When I switch to in game Chat it works. Restarting stadia does not solve the issue. The mic Was working fine 2 days ago. I tried another mic as well. Party chat seems disabled.