oh, if you sign in, and click the email they send you to confirm, there will be a giant list of all the games you bought that it takes you to. i had the same issue, but when i logged into Itch.io it worked out fin
I have been seeing that, except I'm logged in and was downloading from the bundle page, which has worked for everything else so far. I'm on Mac, if that makes any difference, but I don't see how it would. Just tested it on a PC, still shows up 'blank'.
The page "builds" - or put another way, the PDF is not just text. Perhaps your PDF reader (or browser plug in) isn't showing you the final results? Works fine with Foxit for Windows.