This happens randomly and won't happen to every game... Do the follow within X1 settings:
1) Display and Audio
2) Volume
3) Chat Mixer
4) Select anything other than "Mute all other sounds"...pick (preferably) "Do nothing".
5) In-game sounds should turn on instantly
I can confirm that this bug is still present.
I don't know if this was previously mentioned, but in my case there is no sound after I sleep the Xbox... then upon waking the Xbox, ACO has no sound. I have confirmed that the Xbox itself has sound by clicking through the home menu and various other out of game areas. No problem with sound. Only ACO is affected. I have tried changing sound settings and unplugging and replugging the HDMI cable thinking this might reset whatever it is. That doesn't work. Though, the first time I tried getting sound back without restarting, the only thing I succeeded in getting was choppy sound (a small chirp of sound about every 5 seconds).
The only way I have found to get sound back is to kill the game using the Xbox Home screen and the menu button, then restart the game. I tried changing all audio settings in the game to no effect. This problem seems to be triggered by playing the game for some time, sleeping the Xbox One, then waking it back up later.
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Brian
I often run into this problem when I first start the game up, I always leave the disc in the Xbox when I shut it down at the end of play, so when I restart the game sometimes (most of the time for the last couple weeks) I have no sound. The only thing I found to fix it was to restart the console and that seems to reset it for me at least.
Thanks for sharing MstrTarvos. Everyone- if the troubleshooting on this thread doesn't help, please create a ticket. Thanks!