It just wasn't working as described in the instructions
For anything that is not working: open issues on their github repository.
User feedback will help them improve their software!
I may make a small request to add preset windows for contrast/brightness for CT to see brain tissue and to see bone window or metal. That would facilitate electrode localization.
At the moment, I'm using the same logic to display the MRI and the CT images. My heuristic to detect background and elements of interest works OK for most MRIs but not so well for CT scans... I'll put that on my todo list too.
Would you have suggestions on how to proceed?
Thanks for your responsiveness. You are better than any of the proprietary software customer service.
I'll quote you next time we ask money for the software support from the NIH 
Thanks