Trying to implement Azure Active Directory B2C gives me a 404 error

I was having the same issue as well. Some of the things you can check are:

• Make sure the name of the policies in your webconfig and in Azure AD are the exact same, including the correct upper/lower case

• Make sure the AadInstance has a trailing slash (/)

• Make sure you have the latest version of the owin and microsoft.identitymodel.protocol.extensions libraries ( suggest re-loading them from NuGet )

  • This last one is the issue that I had the hardest time finding. If the resulting URL in your browser contains 2 question marks, then this is the fix.

If you're trying to use .auth/me make sure your Store Token is enabled in Authentication Settings. Else it'll give you a 404. :)