Check to see if you are muted (red microphone with line through it) by clicking the microphone icon
Remove the Google Grid View Extension and Manage Extensions
Read & Write (or other installed app or extension) may have disabled your microphone. You may be prompted to change your microphone settings.
Windows:
Unmute your microphone | Google Support Site
MacOS:
Unmute your microphone | Google Support Site
Enable your microphone | Google Support Site