You'll need to elaborate -- that's not much to go on.
What KIND of audio files are these? Are they a different kind than you've used previously?
Since AE has a tough time playing just about anything, please describe in detail how you're playing them.
And it wouldn't hurt to know what has changed on your machine before you ran into this problem.
I have brought in .wav and .mp3 files.- neither will play. They DO scrub on the timeline, however. I cannot even play them when I open them individually. They do play in windows media player and will also play in Premier. As far as I know nothing has changed on my computer. I have even opened previous AE projects that I know played, but no audio on them either. Strange.
CHeck your audio prefs and also the preview and audio panels. Either your audio mapping has changed or you have accidentally muted audio.