Rockband microphone won't show up on macbook?

i just got a new macbook and have been using it for about a week now to record songs with garageband using a rockband microphone. But today i pulled up garageband plugged the mic in and nothing happened. normally a little box pops up and asks if i want to use logitech microphone in garageband and i say yes and it works. but now when i plug the mic in the usb it doesnt show up anywhere on my macbook? maybe some settings are wrong?