Chrome refresh won't work..
When you load the the first time, clicking "microphone" checkbox shows "...wants to use your microphone" dialog.
If you click "Allow", it will work fine.
But if you once click "Block", you cannot use your microphone anymore.
In fact, there are some security issues on using a microphone on a web browser.
This dialog is for blocking a bad site. So if you once click "Block",
Chrome recognizes this page as dangerous and will not allow using a microphone next time.
You can restore this setting as follows.
See URL bar - you will find "Video camera" icon with "X" mark
Click this icon - "This page has been blocked..." dialog will appear
Click "Ask if ... wants to access your microphone" and click "Done"