Try to install the soft for the microphone to the computer and check if the microphone is recording sound with it. Also, check it at another program where you use a microphone such as skype. You can also try to choose the correct device in the game's settings. I play overwatch for many years and never had such a problem. By the way if you want also to get a higher rank in overwatch, but you do not have enough time you can use the overwatch boost. They have professional boosters who would do it for you.