It might have been a temporary glitch. Have you tried another game since then?
Chess.com No Sound
If you have speakers connected to your device, they could be causing the problem.
Try disconnecting and then reconnecting the speakers again if it is the problem. That has happened to me before.

maybe go to setting board and pieces and then turn on sound because for some reason chess.com turned my sound off but now I turned it back on

If your iPad has a ringer switch, make sure it's on.
If your iPad doesn't have a ringer switch, make sure the silent mode setting in the control center is off.

My sound just stopped working on chess.com too, can't hear the pieces move. Strange - i have sound on all other websites

I had the same issue. Cleared the cookies and browing data on Chrome, restarted, and it worked fine. Now, I have incredible lag on my end and cannot seem to fix it. Have installed Windows updates, driver updates, still lagging. I think I've lost 3 games because it looked my opponent's clock was running when in reality, I was losing on time.

I haven't been hearing sound for more than a year. Checked my settings, tried different computers and browsers. Didn't bother contacting support because the last 2 times I did they didn't even reply.

We’re currently experiencing degraded performance issues with our content delivery network . The symptoms of this may include missing sounds and images. Our team is currently working to restore normal performance levels. At this time, approximately 8% of our members may be affected. We apologize for any inconvenience!»
It may affect images loading, etc.
When I was playing a game, chess.com did not make sound when my opponent moved. I checked my volume and it was on. Other sites still work.