Hi there!
If you go into your project settings and look under the 'General' tab, are your Volume Thresholds for your current platform set too high? I've had a few instances where my project automatically set my Mac platform to be at 0, which would prevent all sound under that threshold from being played. I usually keep my threshold around -80dB
Also, on your navigation bar if you click "Audio>Audio Preferences...", is your Master bus set to the correct audio device?
You might have already checked those, but it's always a good place to start!
-Blake