I cannot replicate the “no artwork” problem using the files you supplied.
But that’s a little tricky, as I’m not working with the exact same elements as you are:
You said the flowers are a PNG, but the file uploaded example is a jpg. (Doubt it is as simple as that, but worth noting in terms of trouble shooting)
There is a line of text in your example photos, but is not present in the rectangle or the flowers files. Assuming it is a different file that was added with the “Add artwork” button, maybe that file has a guide line in it somewhere (in which case it would throw an error if you try to move it around the bed), or an element off of the artboard? Use select-all (command-A on a mac) in the GFUI to see if there are any outliers (the blue bounding box would extend off the screen in that case)