Mainstage Sustain Pedal problem

I have a patch in Mainstage with 2 channel strips, and my keyboard (AKAI MPK261) is split in half so that the left half triggers one voice from one channel strip, and the right half triggers the voice from the other channel strip. I'm also using an Alesis ASP-2 sustain pedal. The sustain pedal works fine for the right half of the keyboard, but it won't sustain the notes on the left side. I built another patch the same way (multiple channel strips split in half down the keyboard) and the pedal will sustain the notes on the left and right side perfectly, so I know this is possible. I just can't seem to find the difference between the patch that works and the one that doesn't. Does anyone have any ideas of what could be causing the pedal to only trigger one of the channel strips? I'm using Mainstage 3.5.2, and I'm happy to provide any other information you might need