Voodoo Lab

So I finally got my whole system up and running with a few pedals in the loop of my amp and two channels on the gcp dedicated to channel switching on my amp (Mesa Boogie Single Rectifier). The gcx/gcp worked perfectly switching from channel 1 to channel 2 in my test run. But once I hooked up the last few cables (to the front of the amp, to the effects send/return, and from the guitar to the gcx), it stopped working to change channels. I didn't change anything that was already in place, just added a few more connections. The amp is just stuck on channel 2.

Now here's where it gets weird: when I try to change the amp channel by pressing the appropriate button on the gcp, the channel light on channel 1 flickers, but that's all that happens.

I've tried about a dozen different cables, even a trs cable, and tried using different plugs on the gcx and even different loops on the gcx.

Anybody have any ideas?

Update: The channels changes just fine until I plug anything into the input of the amp or try to set up the second cable to turn on and off the solo boost.