I did a search and couldn't find anything.
 
Anyway, I just installed GTP4. I can record, playback and use various things like GR3, Native Instruments outside of GTP4.
 
But I do not get any input to any of my plugins when I use them within GTP4.
 
I recorded a completely dry guitar track and tried adding Amplitude2 in the effects part of the track on the console pane. It adds it just fine, it's on, not bypassed and I get no input to it while playing the track. So then I tried other things, like the included GTP4 reverb, chorus, etc. etc. I get nothing.
 
Any ideas? Is there some stupid check box I need to click?
I would have expected at least these to work right since they came with the software.

Check your inputs and outputs on each trach and then,try clicking the input echo button.

I agree - check that input echo is "on" on the track and maybe the solo as well? I need that on to have any effect work.