Export video with sound

I have an ActionScript 3.0 I'm working on.  It's an animated Christmas card for my company.  I have an mp3 sound that I edited in Audition CC to match the timing of the ActionScript with a nice fade at the end.  I added a layer for SOUND and dropped the mp3 onto the stage in frame one of the sound layer as it should start right when the movie starts.  When I test the movie in Flash, it plays beautifully WITH sound, but when I export the video and encode in media encoder, I upload to YouTube and the sound DISAPPEARS every time.  I have tried just about everything.  Any suggestions?