I finally got in on my iPad and had the same problem that I had when trying to register for the
Disneyland half - when I was logged in (on my safari browser which has my Disney account saved) it wouldn't auto-populate all of my information when I selected myself. I typed it in, but then at the end it would say I needed to log in, which I would do, and it would spit me back out to fill it in again, just as a loop.
I don't know why this is happening. Has this happened to anyone else or does anyone have a fix? For Disneyland I had to get a new queue on my computer and that worked. The frustrating thing is once it's at the registration screen I can't get it to transfer between devices