I don’t know why Siri has no voice

When I say hey Siri it doesn't work?

Siri might not respond verbally if your device is muted or Voice Feedback is turned off. While you're on the Siri screen, try to increase the volume level on your device. Then check your Voice Feedback settings: On your iPhone, iPad, or iPod touch, go to Settings > Siri & Search > Voice Feedback.

If Siri or "Hey Siri" isn't working - Apple Support