Garageband won't record my voice or anything.

A couple of months ago or may i say nearly a year, i tried out garageband to record my voice. Back then, I was a newbie to this whole apple MAC thing and applications like garageband. So i only would use it to record my voice and i also could change the vocal effects. It worked fine. Then one day, i opened garageband and wanted to record me singing but it didn't work. There's a constant sound of a beat while i record and listen to it after recording. Also, the bar goes totally flatline when i record and listen. The ziz-zag line doesn't come up in the bar. I didn't know what was wrong, i tried to make it work but obviously that didn't happen. So, i left it like that and i didn't bother using it. Though, i want to start using it again for my singing but it still doesn't work.

I would really appreciate some help. 🙂