“The requested content cannot be loaded. Please try again later.”

Hi there,
Recently for no reason that I can determine we get the following message when we click on a thumbnail image in any of our Envira galleries: “The requested content cannot be loaded. Please try again later.” I have included one page as an example. I didn’t make any changes that I know of, yet suddenly it and other gallery thumbnail URLs are not working. Each of the six thumbnails should go to an external page (with information about that particular course).

Can you tell me what happened and how to fix it?

thanks,
Laura K.

The page I need help with: [log in to see the link]