Did Siri stop responding to you all of a sudden? Did it start doing this after a recent update to Sierra? There’s a couple of simple fixes to bring it back to life.
How to Make Siri work again, in Mac OS Sierra?
First, see if turning off dictation will bring Sierra back to life. Go to your Keyboard settings in control panel and turn off dictation. Then, test Siri out. If it works, you can still use Dictation also by turning it back on. If Siri stops after you turn Dictation back on, it means that you unfortunately can use only one of these applications at a time, at least until Apple rolls out an update.
The second option is to simply disable Siri and enable it back again. Though this sounds ridiculous as a fix, it seems to work for a lot of people. To turn off and on Siri, go to the Apple Menu, system preferences and then by selecting Siri. You will see a small checkbox under Siri that says “Enable Siri”. Toggle this on and off to enable and disable Siri. If you are using an external Mic for your Mac, make sure you change your Mic Input accordingly when you go to Siri settings in System Preferences.