Help cropping 4D images after using segmentation wizard

I have a fMRI nifti file of that I need the skull to be extracted from.

I first set up an Image mask using segmentation wizard, to highlight the brain.
After finishing segmentation wizard, I tried saving the masks as .nii.gz files, but when I open the files on my desktop, a folder is created, but empty.

Is there another way to use the highlighted masks to crop out the regions that I don’t want for my fMRI scans.

I have tried different modules to try to crop out my 4D image, but can’t seem to figure it out.