Hi. I have a nifti file which is a volumetric ROI mask output by nibabel. This file is viewable in Freeview and Mango, and is opened without issue using nifti functions in Matlab (nifti; load_untouch_nii) and Python (nibabel.load()). 

When I try to view it in MRIcron, it gives an error:
Unable to read this image format 256

256 is apparently intended to indicate uint8 but is not read by MRIcron. 

Using nibabel, with the file loaded as vol, i was able to do:
vol.header['datatype'] = 8 # was 256

and save the file. it is now loadable in MRIcron.

If compatibility for this datatype is an easy fix in MRIcron, it might save others some hassle. 

Best,
Nick