For some reason, the link you gave for mac doesn't work. This is what is says on the page "This XML file does not appear to have any style information associated with it. The document tree is shown below."
Have you updated the xml files? Some cards doesn't recognize like some of the KtK cards like Narset (which came out as the back of the MtG card).
I "manually" fix in the pic folder with an actual card image (ie Narset or Surrak) but when I choose that card, it went blank. I usually do that to other cards when I like the modern look over the classic look and it shows in the program.