Microphone audio is not recorded
If Screencastify does not record from your microphone, make sure the microphone level indicator inside Screencastify shows any activity. If it does not, the microphone might be muted in your system settings.
If it works in other Applications, but not in Screencastify, please check if it works in other web applications inside Chrome. You can try this Demo, it is supposed to show activity when you speak. If it fails with other web applications inside Chrome as well, re-starting your Computer might help.