Copying @Ocaasi_WMF bug report verbatim:

1. I click the link from Wikipedia: https://wikipedialibrary.wmflabs.org/partners/16/

2. It gives me an adorable Permission Denied page with a hamster!

3. Telling me to log in, I do so in the header. It sends me back to Wikipedia where I give OAuth permission.

4. That sends me back to the Library Card login where I select my language from the dropdown.

5. That sends me to my user profile.

There are obviously several things we can streamline here, but the minimum-viable outcome should be that after logging in I am returned back to the McFarland signup page. Extra clicks are not a huge annoyance unless they don't lead to completion.