Why won't my Pro Tools M Powered record?

First of all: this isn't my first rodeo with pro tools. I used to use LE, but I've recently down-sized my studio and started using an M-Audio interface. So naturally, I bought M Powered. I created the track, record-enabled it, and all of my connections are correct. For some reason, it shows up in the mixer when I play into it, but when I record it doesn't record the sound. I can hear it through my monitors and headphones and it registers on the mixer in pro tools. Why won't it record?