Why wont my Xbox 360 mic work?

how can i fix it i ordered another Xbox 360 mic because the one that came with the Xbox broke after a couple months of using it and so i got another one its mostly black but the part you talk into is green and the back of the ear piece is green also and when i ever i try to use it now i cant hear the other person but they can hear me what can i do to fix this Thanks! and ill give ten points and thumbs up