Lets assume you are using Google Chrome on that Android. If you are not, it might not be the same. But if you have Chrome, lets try that.

  1. On the browser top bar you will see three vertical dots. 
  2. Tap those, a menu will open. 
  3. On the top of the menu there will be an i in a circle (i for information). Tap that
  4. You should see a notice about mic allowed or blocked. And on the lower right "site settings". Tap site settings
  5. On the screen that opens up, there is a "permissions" section. You can tap on the mic permission here to deny or allow it.