Landing/Startup Theme iPhone not overlaying over header background

I’ve tested out the Landing/Startup Theme, but the image of the iPhone is not overlaying over the background header image.

I loaded the Demo data and imported it fine, but the formatting of the landing page does not look exactly like the demo site where the iPhone image has a higher z-index than the header background parallax image.

Can you assist with how I can adjust this to make the iphone image overlay on top?