Won't playback from beggining

All of a sudden, in the middle of the project, when I press my key command to go back to the beginning of my song, and press play, it doesn’t playback. The cursor doesn’t move and no audio is played back. If I move my cursor anywhere else and press play, it works but not from the beginning. It also doesn’t record from the beginning of the song but every where else it’s fine. Can somebody please help!