Animate won't allow me to change audio sync to "stream" it only allows "event" from the dropbox in properties

I've watched several videos of people importing audio in Adobe Animate CC. I follow everything they say until it gets to selecting "stream" instead of "event" on the properties menu. The dropbox that has "event" checked/selected won't allow me to click anything else. I'm probably stating the obvious to those who know, but I need to select "stream" because it will allow me to manipulate what I'm animating as I go and have the audio synced with mouth movements. With "event" selected I can only hear the audio when I play it from the beginning and not at all after I pause and unpause. I've tried WAV and MP3 files for the audio to see if that might have something to do with it, but it didn't. Thanks a lot to anyone who might have an answer I'm sure I'm not the only one who's ran into this.