Howdy-

The Bob is out today, so I will take a crack at this...

For reference, I am looking at the InstaCorr and GroupInCorr demos in the Bootcamp data:

cd
curl -O [afni.nimh.nih.gov]
tar xvzf CD.tgz
cd CD
tcsh s2.cp.files . ~
cd ..

... with the relevant part of the unpacked directories being:
~/AFNI_demos/AFNI_InstaCorrDemo.mini/vol
... where there is the "@RunVolGroupInCorr" script.

From your error message about ports, I think that the niml-talking functionality has not been actuated. Looking in the @RunVolGroupInCorr script, I see:

afni -niml -npb 0 -yesplugouts -layout DemoLayout
sleep 1
3dGroupInCorr -npb 0 -setA G1.grpincorr.niml -verb &

You do have "-niml" running; do you have another instance of AFNI and/or SUMA up, by any chance? If you do, there might be port number confusion. You can specify a port number for communication explicitly with both the AFNI GUI and 3dGroupInCorr with "-npb SOMETHING"---in the above, it is "-npb 0".

Can you try 1) closing existing AFNI/SUMA instances, and 2) using "-npb NUMBER" with the same NUMBER for both the GUi and 3dGroupinCorr?
(The "sleep 1" might or might not be so useful; kind of depends on the system---gives AFNI a bit of time to setup before running 3dGroupInCorr in the demo script.)

Just some other AFNI/port functionality---
instead of closing existing AFNI/SUMA sessions that might be using a port, you should be able close just ones that might be using a particular port number, to make sure there is no crosstalk:

@Quiet_Talkers -npb_val NUMBER

--pt