Voice directions not working.
First, ensure that you are using the unmuted internal speakers by pressing the power button twice while the unit is on.
Do you hear beeps (button tones) through the speakers?
These are a couple things to try:
1. Change the voice from English TTS (JILL) to English TTS (JAKE) - This will demonstrate whether the voice database has been corrupted.
2. Tap the power button twice while the unit is on to switch back to fm transmitter and attempt to use your radio to tune the sound. If you succeed here, you may indeed have a problem with your internal speaker. A return of the product may be necessary.