Upcoming Events background image not shrinking on mobile

On dev.LennyPey.com, on the Upcoming Events section, I am using the demo photo provided by the Catch Themes Pro team for the background image. On a computer screen, the background image looks great and is full size. (Showing the hands up in the air in black and grey.) On mobile devices, all you see is a black background. Can you help me duplicate what is seen on a computer screen? I believe the image needs to be shrunk down, but since it is totally black, I'm not sure I'm even seeing that demo photo. Many thanks for a super great Theme! Julie