This is probably a bug/regression?

https://test.musicbrainz.org/artist/create doesn't work because,

Unauthorized Request

Sorry, you are not authorized to view this page.

You must first add and verify your email address before being able to edit or add anything to the database.

Going to do so, you see,

Warning: This is a development server. Your email address is not private or secure. Proceed with caution!