Open Firefox and play content

that should play sound, such as
this Firefox video or a Flash video with sound

Click the volume icon in the Windows taskbar, Make sure the sliders for Mozilla Firefox and Plugin Container for Firefox (for plugin content such as Adobe Flash) are not muted or at the bottom.

This does not help. It is on iPhone. It will play the audio for like 30 seconds when the app is minimized or phone is locked but then the audio stops. Volume is up nothing muted. When you reopen Firefox app it will start playing again, but when you leave the app it only plays for about 30 seconds in the background

I have the exact same problem... Still no fix for this?