Upgraded plugin and thank you pages 404 now

my site is chipin.anjelliclecats.org

I upgraded from 2.16 to 2.5 and now my thank you pages 404. Everything else seems to work.

There's nothing weird about my config, but I did customize the slugs. The thank yous should be at: /donate/apt-fire-cats/thank-you/ (apt-fire-cats) is the name of the fundraiser.

Please help bc my site is basically crippled now.