Dear Richard,
It is still not entirely clear to me what might be your problem, but I have a few considerations:
- I opened your
dualct2.flairfile and I found that theVOXELcard had a wrongfilename, I chaged it alternatively to the two.vxlfiles you provided (default.vxlandnewconver.vxl), however, also for me the voxel regions did not have a material assigned → there might be something wrong with both files. - Then I decided to create a
.vxlfile from scratch starting from a dicom example file that I found on the web (.dcm), to test yournewconver.matfile:-
first I used for the material definition
head.mat(a file provided in the Flair webpage, in section Auxiliary files) → this worked fine and created the desired geometry (see picture below)

-
then I used
newconver.matand in this case I got the same error message you are receiving (se picture below).

-
To me, there is something wrong with newconver.mat, but also probably with default.vxl and newconver.vxl.
Can you please try to re-generate your .vxl file starting from your dicom file and using, for the materials, head.mat (download it from the Flair webpage, in section Auxiliary files)? To create the .vxl file, I would suggest you to follow the steps provided in this thread: RT-planning example using Fluka.
I hope this can help you,
Cheers,
Marco