How to get the timeout warning sound?

According to the forum, other people have the same issue, but I didn’t see if it can be resolved:
Supposedly, there should be a timer countdown warning sound, but I don’t hear it. I can hear the stone placing sound. This really bothers me, I just have lost two games on time.
Are there any suggestions? Can this be related to the browser or device? I am using an iPad1 with Safari.

We know there are issues on the first generation ipad that there’s not much we can do about… it’s no longer supported by apple and a big challenge for us to try to work around since we don’t have one.

I had the same problem using Chrome 51 on a Pixel C tablet (Android). I could hear stone placement sounds but there was no audible warning for timeout.

I’m using Chrome for Android and just lost a game because there was no audible warning for byo-yomi time periods elapsing. I have the feature turned on in options. This problem is not consistent, other times there have been warnings but this time there was nothing. Something else I have noticed is that often I get sound when I play but not when my opponent plays. For me, unreliable sound is a big issue. I hope this can be fixed soon. I attach a screenshot with details of my software & hardware. Thanks for your attention.