If you are using an iPad, we have found that content blockers enabled in Safari can cause this issue. To disable content blockers, go to Settings, find Safari and tap Content Blockers to disable extensions. Then, also try to toggle the mute switch if your device has one.
Safari recently made a policy change about playing audio through web browsers so if the steps recommended above do not resolve your issue, please try using a different browser such as Chrome or Firefox. You can download Chrome by visiting www.google.com/chrome or Firefox from the Apple App store at https://itunes.apple.com/us/app/firefox-web-browser/id989804926?mt=8.
If you are not on an iPad, please contact us and let us know what type of device and version of browser you are using, as well as a specific game for which there is no sound. This will help our technical team pinpoint and correct the issue.