Can't update Riot Account

Exact steps:

1. Went to https://update-account.riotgames.com/
2. Logged in.

And instead of being logged in, I am instead greeted with the wonderful message of... https://cdn.discordapp.com/attachments/298960050964267011/656415455988285441/unknown.png

So I can't actually do the thing that I want to do -- you know, update my account log-ins.