When editing I usually have things set up to where I have the Gl2 hooked up through FireWire, use FCP to edit, and have the GL2 connected to the TV via RCA. Sometimes this makes it so that what I edit shows up on TV - this is incredibly helpful. However recently, this has not been happening and I have no idea why. What settings should I enable, what should I do?

You should first look at what has changed. If it worked previously,
it should work now as well.

Camera needs to be in VCR mode and you need to tell FCP it
needs to output over firewire and preview there. I have no idea
how to do this since I'm not on the Mac platform.

Also take a look at this thread:

http://www.dvinfo.net/conf/showthread.php?s=&threadid=38744