Can’t show images

I’m trying to make this work but it seems something is conflicting with the css. The grid or whichever option I choose, doesn’t show the featured image. But the overlay works fine and with the desired settings (opacity, color, etc.).

I have even tried to paste the whole visual portfolio css into the “additional CSS” part of the theme, didn’t work.

Any suggestion is highly appreciated!

The page I need help with: [log in to see the link]