Mute switch on iPhone 4 not working

[myroomismessy]

I had to replace my iPhone 4 screen after I dropped and cracked it, and afterwords my mute switch has not been working at all. My phone is stuck on "sound" mode and I can't get it to "silent" mode by using the switch. My vibrator motor, volume buttons, headphone jack, speaker, microphone, earpiece, etc. all work fine, it's just this one bit that isn't working. Any ideas on what could have gone wrong in the install/how to fix it? I used ifixit's guide to replace the screen.

Thanks!