Check in the game itself if the microphone is enabled and configured correctly. Make sure no other programs are interfering with its operation. If it doesn't help, try connecting the microphone to another device for testing.

Check the settings in CS2 itself to enable the microphone. Make sure your microphone is selected as the input device. Also check if the correct drivers are installed and no programs are blocking the microphone's functionality.

Maybe in CS2 itself there's a button you need to press to get the mic working? Check it, sometimes you have to select the communication mode or enable something else. Also look for privacy settings, maybe something is blocking it there. Otherwise, if it's new, it might just be defective, go over to your friends' place to check for sure.

Try to make sure that in the game you actually turned on the microphone in the settings, sometimes it may be turned off, also check if the drivers for the microphone are installed correctly and if any other applications that might be blocking it are closed, and if that doesn't help, check if something is wrong with the cable or the contacts themselves.

Maybe something is wrong with the voice chat settings in the game itself? Try changing the input device there to check, or look in Windows sound settings to make sure the microphone is activated.