In order to practice your speaking skills, please give Duolingo permission to access your microphone on Google Chrome. If your issue is not with your Google Chrome browser, you may want to check the article My microphone is not working. How can I fix it?
Fixing the issue on Google Chrome
The first time you use Duolingo in Google Chrome, you will be asked to allow Duolingo to use your mic. You should see the following prompt from the top left, and you should select "allow".
If you accidentally "Block" Duolingo from accessing your microphone, your speech challenges that involve microphones will not work from now on. There are two easy methods you can use to edit your microphone permission to re-allow Duolingo to access your microphone.
1) When you are in a speech challenge that requires a microphone, you should be able to find a video camera icon at the end of your browser's address bar. Click the recorder icon on your address bar, choose "Always allow https://www.duolingo.com to access your microphone," then click "Done".
2) Another way to fix this is to click "Secure" right next to your browser's address bar. You will receive a pop-up with a drop-down menu for Microphone settings. Click "Allow" and then reload the page to upload your updated settings.
And that's it, you'll be good to go!