It is a requirement the image be clicked on, it is also a requirement to have the window pop up.
I think the caption isn't showing because the image is being brought up by URL. On this site there are images saved to the servers that are being called and images called by URL. The images on the server pop up in the window with the caption showing, and the images called by URL do not.
Is this clear?
PS. No one will be connecting via phone as this is in-classroom material