You need to clear all of those keyframes. Extend a single frame without adding any keyframes or every time you create a new keyframe you're wiping out the audio.
So remove all frames except frame 1 where your audio should be. Click inside frame 1. Press F5 to insert frames and you will see the frame is extended without creating a new keyframe. You could also hold CTRL and hover your mouse over the right edge of a frame which will turn the mouse cursor into a left/right arrow, then left-click and drag the right edge of the frame out.
When the frame is stretched out with no extra keyframes you will see there is a waveform depicted:
Thankyou so much! Now I can get back to animating!
One last thing (sorry): When I press play from any frame, the audio starts from the beginning (not the timeline, the mp3).
Sorry, I'm a bit of a noob at this.
If you set the setting to Stream as depicted in my first response the audio should start where you expect it. If it's set to "Event" (default) it will do what it's doing now, starting from the beginning no matter where your play head is. Did you set it to Stream?
I see you mentioned in a different thread you were encountering the old bug that requires you to start Flash as Administrator as one workaround for this audio issue. Nevermind
You're welcome and good luck!