Intensity segmener

Hi
I am having a problem with the intensity segmenter tool with some files /not all/… once I open a .giple file it wont let me put any thing in input/volum so I can not hit apply to creat segmented model.

I also noticed that the background is gray.
While in other i have bkack background.

Attached is screen shot of the problem.image
The second one is when it is working correctly
image

Thank you