When I import images from an external drive into Digital Image Suite Library it shows all my folders and place holders for all my images but I don't get thumbnail previews. Can anyone help me figure out how to get the previews to show?

What I find really odd is that out of a folder of 40 images,1 or 2 of the thumbnails will show but none of the rest.

When I was accessing these images from my internal drive all of the thumbnails were there. I copied the files to the external drive and now most of the preview images don't show up. They are there when accessing from the internal drive but not there on the identical files on the external drive. I imported them and see where they should be though.

Thanks, I appreciate the help.