Issue with Embedded Audio in Adobe Express PDF – Not Playing in External Browsers

I uploaded an audio file as embedded media to a PDF created with Adobe Express. On the editing page of the Adobe Express site, the audio appears correctly and plays without any issues. However, when I share the link to the published PDF and open it in an external browser, the audio does not play. Even after pressing the play button, it only shows a loading screen and never actually starts playing.

At first, I thought the issue might be with this particular file. But I tested a different Adobe Express PDF with embedded audio that I created a few weeks ago—one that used to work perfectly—and found that it now has the same problem. The audio no longer plays through the shared link, even though it worked fine in the past. This audio was recorded using my iPhone. I need to submit the PDF as part of an assessment task, so I'm very concerned. I would like to know what exactly is causing this problem.