I had the first gen Chromecast and it worked perfectly for years then about a year ago suddenly I just had no sound one day. I thought maybe it has reached its use by date as it was getting old so i threw it out. Yesterday I bought the new one and set it up and it too has no sound. I checked all the settings on my tv and in the Chromecast settings and in the device in Google home. I followed multiple videos with fixes. Nothing worked. I tried on another tv and same problem. I did factory reset but still no good. I wasted hours of my time trying to get it to work which is really frustrating. If it's some hidden setting somewhere then that is just ridiculous and Google need to address the issue. I really enjoyed using the old one for many years until it stopped working. Anyway I'm taking it back for a refund as it's useless and I'm not willing to waste any more of my time on it.
I understand not being able to use your Chromecast properly isn't the best experience. Rest assured that we'll take note of it — we'll ensure that we'll learn from your experience as we continually improve our products and services.
Let us know if you have questions and concerns otherwise, I'll be locking the thread after 24 hours.