I had issues with accessing MoveUp but tried several things and eventually got it to pull up. I'm the primary person on the reservation but searching with my last name didn't work. I read a comment on here suggesting to give the last names of other people on the reservation a try if there are different names. Using my spouse's last name and reservation number pulled it up.
Additionally, I can't get it to work on my desktop browser on my computer, but it works just fine on my phone. I sent myself the link and then pulled it up on my computer without issue. It's super weird. If you have only used your computer to try, try doing it on a smartphone.