Your flexible layout options are making the images collapse down to 0 width/heights. This is because you have the pins set to preserve the margins (meaning all pins are set).
There's a new flexible layout mode in Hype 3.5 that can better preserve position and scale; you do this by unchecking all the pins. This will be closer to what you want.
Most likely though you'll just want to put everything within a group, and then use that same setting on the group (with 3.5's other new feature, Zoom Contents checked).