Before we being, make sure you are actually using Google Chrome or Microsoft Edge. Dictation does not work on other browsers! It does not work on Chromium / Firefox / Brave / etc.
If your microphone access is blocked to Voice In:
Step 1: On the Voice In Options page, click on the little icon with the red dot in the address bar as shown below: (it is either a microphone icon or a video camera icon depending on the operating system)
Step 2: Change the setting to allow access to your microphone:
Step 3: Click on the "Allow microphone access button"
If you did everything correctly, it should change to
That's it! You have now enabled microphone access for Voice In to work.