Google has introduced a change that affects how volume is controlled on Google Cast speaker groups.
If you are using the Speaker Group feature to control the volume in the Google Home app, by voice with the Google Assistant, or directly on a Nest Hub display, you will notice a few changes:
- You need to adjust the volume of each speaker individually instead of using the group volume controller.
- You are no longer able to use your phone’s physical volume button.
See more here:
https://support.google.com/chromecastbuiltin/answer/6328714?hl=en&ref_topic=6372841
