Steps to reproduce
1. As an archivist, import a work for an email address that does not belong to an existing AO3 account, but that you have access to
2. Log out
3. In the "Invitation to claim works" email, follow the "Claim or remove your works here" link
4. On the "Claiming Your Imported Works" page, there will be two buttons that say "Sign me up and give me my works! Yay!" – use the second one, which is beneath the list of imported works
The account creation form/page doesn't load. The exact behavior of it might depend on your browser, though – in Safari 10.1.2, I get a white page. In Chrome 60.0.3112.113 , I think I instead got a grey page with a warning from Chrome, but I didn't write it down. /o\
What should happen
You should be taken to the account creation page, as you are when you press the top button.
The top button:
The bottom button:
The bottom needs to be a GET, too, or else the route needs to be updated.
Natalia Gruber made an archivist account and imported a work for a disposable email.
I got the email, followed the "Claim or remove your works here" link, the clicked the second "Sign me up and give me my works! Yay!" button, which leads me to the "Create Account" page.
I filled in the form, signed up, got the activation email, activated the account and logged in. The new account has the imported work: https://test.archiveofourown.org/works/1069396.