With an hour or so of floundering around, I managed to succeed. Although I was recognized and automatically logged in, I was not allowed to edit wikis. So I logged out, tried to log in, said I had forgotten my password (which was untrue), got a temporary by email, used it to login, changed my password (back to the old one), was finally allowed to edit my preferences, made no changes, clicked OK, and was now allowed to edit.
Is all that hassle really necessary?