Rain Voice Note Web App only works in Google Chrome, as it uses the Google API.
Microphone Permission for Rain Voice Note
Click the Microphone icon.
Click on the red-crossed camera in the right corner of the Chrome address bar.
Select Always allow https://nvjob.github.io to access your microphone.
Click on Done. Reload app.
This will only need to be done once the first time you use the web app.