We advise you to check this article if you are using wireless headphones.
Please check if the microphone is enabled in your game session.
In the browser: exit full-screen mode and put the toggle switch to the right:
You can also change the input device that your browser uses in its settings. For example, microphone settings can be directly opened in Google Chrome via this path:
chrome://settings/content/microphone. Alternatively, you can go to Settings - Privacy and security - Site settings - Microphone
In the PC application: open the menu by pressing CTRL + F2 (Windows & Linux) or holding ESC (MacOS). Make sure the microphone icon is not crossed out and the volume and sensitivity is not set to 0:
You can also test the input device in the application settings.
In the mobile browser: flip your phone to portrait mode and make sure the microphone icon is not crossed out:
Additional ways to solve the problem:
Open Steam settings (From the top left, click on Steam and select “Settings” in the menu that opens)
In the new window, select “Voice” on the left
Make sure you have “default” or “MIC 2” selected as input device
Scroll down and open “Advanced Options” by clicking on the “Show” button
And try turning off “Echo Cancellation” or “Noise Cancellation”
