Check if your microphone is set as the default device in your computer's sound settings. Then, make sure the mic is enabled and selected in Valorant's settings. You can do this by going to Settings > Audio > Voice Chat in Valorant and ensuring the correct microphone is chosen. Also, make sure that your Input Volume isn’t too low.
Alternatively, this issue may be caused thanks to a very common glitch that makes it so that players don’t see the microphone option on any teammate. The best way to fix this is by restarting the game as that also resets the in-game voice chat feature.
Verify your Output Device in Valorant's Settings > Audio > Voice Chat. Make sure the selected device is the headset or speakers you’re using. Check the volume slider as well; if it’s set too low, you won’t be able to hear teammates. Additionally, ensure that the in-game voice chat is not muted.