Tck2connectome after tcksample gives an error


I am trying to generate FA-weighted structural connectivity from two self-defined ROIs. When I ran the following command the streamline counts can be generated without issue:

tck2connectome -symmetric -zero_diagonal tracks_10M.tck parcellation.mif parcellation.csv

But when I tried the following, it gave an error saying one of the region was not assigned any streamlines:

tcksample tracks_10M.tck fa.mif mean_FA_per_streamline.csv -stat_tck mean

tck2connectome tracks_10M.tck parcellation.mif mean_FA_connectome.csv -scale_file mean_FA_per_streamline.csv -stat_edge mean

I checked the registration and it looked fine.

I really appreciate any advice on how to resolve this.