From the pics, it looks like either the pdf is loaded directly in an iframe or it's embedded with application/pdf via object or embed. It doesn't look like it's a direct link to a pdf in the address field. The other two should work too, but perhaps they're not for some reason. Any adblocking extensions?
I'd right-click on the the area where it's supposed to load and inspect the element to see the source/markup that's trying to load the pdf.