My Layers are not Showing in Preview?

I am not sure if anyone reads these old posts....but here it goes. I am having exactly the same problem. This has nothing to do with objects grouped and/or the position on the timeline because I created a very simple file to test this issue and it shows up here as well.  I have a base layer with one or two text boxes. I created a new layer with 2 pictures that have triggers that move fwd and back 1 slide.  when I preview I can not see the images. I checked position in timeline, position of layers, visibility settings - nothing seems to be out of place.  This also happened with a text box (preview and can't see the text) but I put a border around the box and it was visible on preview.   I am posting the file.

Related question: is there any way to copy a layer from 1 slide to another?  thanks!

Robin