I've had this problem a long time. I can't hear any of my mp3-files in my Flash Professional CS6 anymore.
Over a half year ago, they worked normally. I started to use mp3-files in my animations to learn lip-syncing. I was able to hear them in the animation and in the test.
Then something happened. My graphics card had to be changed, cause the other one's fan was making annoying noise. We bought a new one, which didn't work in my computer. I had to use the old one until my computer was rebooted. Then I got a bit worse graphics card but it's working at least. I'm not sure is it about this, but nothing bigger things happened that could've changed something in Flash. o_o
Before that I remember that my Flash was working normally. :/ I've been trying to find the solution everywhere from Google, but nothing hasn't helped. (Or then I've missed it, because English is not my native language.)
Let me share you some screenshots.
I can normally import mp3-files into my library. (I make them .mp3 in Sony Vegas Pro 11)
I can add them into the timeline.
But. When I test the animation in timeline or in the "Test Movie"-thing, no sound can be heard.
In this file, I have this kind of settings.
When I try to test it in library, I click Play-button. I can't hear anything and the Stop-button shows up in under a second. It just zips a split second, I can't even click on it because it happens too fast.
That's probably all I can show.
I've only used sound for lip-syncing in Flash, then later added the animation and the sound apart to Sony Vegas.
I use Turtle Beach Ear Force X12, which are working normally. I used them when was able to make lip-syncing animations.
I have Windows 7, 64 bit.
Ask me anything if you need to.
I would love to get help for this, thank you. (: