Voice commands on Moto360 not working... sounds like might be having an issue with your Moto 360 microphone. Has it ever worked for you? Try tapping on your screen and saying "Call [name]" to see if it picks anything up.
First thing I would try is reboot your moto 360:
Reboot: Touch the screen twice, then touch Settings > Reboot.
Factory Reset: Touch the screen twice, then touch Settings
Caution: Factory Reset clears all settings and information about the current paired phone, so you can pair your watch with a different phone.