Symptoms

WIF10201 No Valid Key Mapping for X509SecurityToken
 

Diagnoses

WIF10201: No valid key mapping found for securityToken: 'System.IdentityModel.Tokens.X509SecurityToken' and issuer: 'https://sts.windows.net/79762414-1af0-4210-8461-ebee9086446b/'.

We checked the federation metadata document for the STS, and found that the thumbprint we were using did not match the X509 certificate listed in the federation XML. We copied the certificate into notepad, saved as a .cer file, and found that our thumbprint in our claims configuration did not match.

Once the claims configuration was updated via the claimissuer smartforms in designer, the issue was resolved.
 

Resolution 

This was caused by an incorrect thumbprint for the issuing security token service. Once the thumbprint was updated with the correct one, the issue was resolved.