apologies for the n00b question, but I've found information sporadic on this one. I've been making an API using MVC Web API and have been using forms authentication as described in the SO selected answer here: ASP.Net MVC 4 WebAPI Authentication
As expected, the auth cookie is sent in the response header at login. However, when I then try a method decorated with [Authorize] after this, the request does indeed seem to include the auth cookie in the header, but I get a HTTP 401 every time.
The sources I've read indicate it should be almost trivially simple, so I'm actually not sure how to debug this one. How can I make sure the auth method actually works?