WIF10201: No valid key mapping found for securityToken: 'System.IdentityModel.Tokens.X509SecurityToken' and issuer: 'http://xxx/adfs/services/trust'.
This is with ADFS 3.0 and the base VS 2013 with ASP.NET MVC.
Long discussion with Mr. Google - many entries, many explanations - "remove the trailing slash" , blah, blah, the most bizarre was "This is because WIF doesn't support SAML".
Yes - that statement's true but WTF does it have to do with the problem?
Google quality is getting exponentially worse and worse.
I knew this error rang a bell and after some quite reflection I remembered why. Vittorio had mentioned it:
His article didn't apply in my case because I get the error straight away - the home page doesn't display so there's no "Sign up for this application" link.
The article goes on to say that this "issue will be fixed soon".
So I took a punt and upgraded to VS 2013 Update 4.
Created a new project - problem solved.