Keynote won't load background images from converted powerpoint

I use pre-made powerpoint for teaching. I usually download them from the internet and my Macbook converts them into keynote. For some reason just today, it started loading the text but not the backgrounds. I can download it to my iPad in keynote and it converts fine. If I save it from my iPad as a keynote to dropbox and open in keynote on my Macbook it loads fine. I'm guessing it's a setting somewhere in my macbook but where? Anybody know?