Did you every solve your image loading problem? I'm running into one myself ... I open a Zeiss .czi stack in ImageJ/FiJi, and saved it (from ImageJ) as a TIFF stack. When I open it in Neuromantic (v1.7.5 or v1.6.3), NM shows a black rectangle of the appropriate dimensions, and appropriate number of z slices, but they are all black. Adjusting the min/max lookup sliders has no effect. I tried a bunch of things like reducing the TIFF file size, reducing from 16-bit to 8-bit, even saving a single image from the stack as its own TIFF file. None of this helped.
First I thought it was a problem with running NM under Windows 10, or some other compatibility issue with my computer.
But then I made a very simple TIF stack in ImageJ, just drawing by hand a few sketches in each of several planes. Saved that as a TIFF, and it loads just fine in Neuromantic, and it looks right. So it doesn't seem to be a fundamental problem with my system particulars, since it can display some TIFFs. Odd.
In summary: some TIFFs show up correctly, others remain blank.