Can't Get a Signal To TH3 Guitar Plug-in

I bought the TH3 Guitar modeling software, and if I run it as a stand-alone application, it works fine, but when I use it as a plug-in in Logic Pro X, the plug-in window appears, but it doesn't see any signal whatsoever from my guitar. No input signal, and of course no output. The plug-in is fully registered.

Here's what I'm doing:

1. I create a new track

2. I choose "Software Instrument" from the New Track window that appears

3. I choose TH3 for the Input.

4. For the Output, I choose 1 + 2

5. Then when the track appears, in the center column, I click on TH3 to bring up the plug-in window, and it appears, but when I play the guitar, there's no input. No LEDs moving. Nothing.

I know it's probably some little thing I'm doing wrong (I'm new to Logic Pro X), so if I missed a step (or I'm doing too many, or something too soon) I'd be very grateful for the help. 🙂

Thanks - Scott