If you are on a website (such as SmartyAnts), you may need to enable your microphone. 

The following instructions will explain how to enable to microphone within Chrome browser / on your Chromebook.

1. Select the lock icon to the left of the address in the address bar. A drop down box will appear with an option for Site Settings at the bottom. Select the Site Settings option.
2. In the Site Settings, locate Microphone.  Change the preference to the right of it from Ask or Block to Allow.  You may need to reload the page afterwards but your microphone should now be enabled for that site.