Symptoms

K2 Smartforms Runtime and ADFS
 

Diagnoses

WIF10201: No valid key mapping found for securityToken: 'System.IdentityModel.Tokens.X509SecurityToken' and issuer: 'http://DFEPOCADFS.DFEPoC.local/adfs/services/trust'.
More Details
at System.IdentityModel.Tokens.SamlSecurityTokenHandler.ValidateToken(SecurityToken token)
at SourceCode.Security.Claims.Web.WIFExtensions.SamlSecurityTokenHandler.ValidateToken(SecurityToken token)
at System.IdentityModel.Tokens.SecurityTokenHandlerCollection.ValidateToken(SecurityToken token)
at System.IdentityModel.Services.TokenReceiver.AuthenticateToken(SecurityToken token, Boolean ensureBearerToken, String endpointUri)
at System.IdentityModel.Services.WSFederationAuthenticationModule.SignInWithResponseMessage(HttpRequestBase request)
at System.IdentityModel.Services.WSFederationAuthenticationModule.OnAuthenticateRequest(Object sender, EventArgs args)
at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Booleanand completedSynchronously)

It would appear that the Realm and ADFS Federation Configs are Case Sensitive . Your Realm Entries need to match 100% with the ADFS Relaying Party values
 

Resolution

Updated Identity.Claims* tables and ensure that all the Realm and Issuer entries matched the ADFS Fed and Relaying party configs exactly including CASE