If you can't hear one person's snap story, it might be that your device's speakers are faulty. Try playing other audio to test. Or, you could uninstall and reinstall the snap app to see if that fixes the issue.
You could try checking your phone's volume settings or making sure the snap app has the necessary permissions.
Maybe it's a problem with your internet connection. So, first check if your Wi-Fi or data is working properly. Also, see if the person's snap story was recorded properly or if there was some glitch on their end.