Error While Using An Atlas

I was also able to get the reduced connectivity (coh) matrix for the source after applying PCA on each scout.

This looks very noisy. You will need to run some group-level statistics to extract some meaningful information.

I have another question - is there a way to arrange the regions in the order I want in the connectivity matrix?

This is something you'll need to do manually with a Matlab script, by changing the order or the rows and columns in the following field of the connectivity file: RefRowNames, RowNames, TF.