I don't think you understand. I'm referring to live streaming broadcasts, not playing mp3's. And my Firefox doesn't even seem to know it has the plugin on it, even though it does!
Well it’s not that I don’t understand how they work.....it’s pretty straightforward. You have a media/file type you wish to play, you specify the app. that will play it in FF. Some, as you’ve pointed out, require plugins and you say you have the requisite plugin. I assume you’re using the latest version of FF.
Usually the best approach is look at “what changed from when it worked to now” and work from there. Did an older version of FF or the plugin work? Did an update screw it up? If so, downgrade to an earlier version, etc. It’s not rocket science; it’s usually an issue of proper versions/combinations of browser, plugin(s), viewers, etc.