Here is a list of things you should check in order to get sound to play in presentation mode:

1. Verify if the sound is present and loud enough in slide edit mode.
2. Check if any external devices (speakers, wireless audio, etc.) are properly connected.
3. Check audio settings for the computer (Input/Output devices, Sound Volume, etc.).
4. Verify if the presentation file has stored an audio clip.
5. Re-verify if the sound is present and loud enough in slide edit mode.
6. Restart PowerPoint.
7. Re-check audio settings for the computer.
8. If there are multiple audio files playing on one slide, review all audio clips.
9. Inspect the audio transitions and audio effects.