Solution 1 - Follow these steps carefully.
Reinstall Dirac Live once more (no need to use the uninstaller).
Do not start Dirac Live straight after the installation (uncheck the box to start Dirac Live after installation)
Restart the computer
Now start Dirac Live
Solution 2 - Check so the microphone has full access/permission to be in used inside Dirac Live.
Windows users:
Privacy & Security settings -> then select “Microphone” and make sure it is set to allow access. Both in general and that apps also have access.
Also have a look at System -> Sound -> then select Microphone. Access must be set to “On” or "Allow" (the text you see should read "Don't allow")
Mac users: macOS System Preferences => Security & Privacy => Microphone => Dirac Live => ON