RDWEB and OKTA integration using SAML based Authentication

We are getting below error while trying to do RDWEB and OKTA integration using saml based authentication.

Getting below error. while trying to follow this technical article. - How to set up SSO to Microsoft Remote Desktop Web Access (RD Web) with Okta

ID1054: The IClaimsIdentity did not contain a valid UPN Claim. The automatic Windows identity mapping feature requires exactly one non-empty UPN Claim to be provided.

ID1054: The IClaimsIdentity did not contain a valid UPN Claim. The automatic Windows identity mapping feature requires exactly one non-empty UPN Claim to be provided.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.IdentityModel.Tokens.SecurityTokenException: ID1054: The IClaimsIdentity did not contain a valid UPN Claim. The automatic Windows identity mapping feature requires exactly one non-empty UPN Claim to be provided.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[SecurityTokenException: ID1054: The IClaimsIdentity did not contain a valid UPN Claim. The automatic Windows identity mapping feature requires exactly one non-empty UPN Claim to be provided.]
   Microsoft.IdentityModel.Tokens.WindowsMappingOperations.FindUpn(IClaimsIdentity claimsIdentity) +577
   Microsoft.IdentityModel.Tokens.Saml2.Saml2SecurityTokenHandler.ValidateToken(SecurityToken token) +419
   Microsoft.IdentityModel.Tokens.SecurityTokenHandlerCollection.ValidateToken(SecurityToken token) +127
   Microsoft.IdentityModel.Web.TokenReceiver.AuthenticateToken(SecurityToken token, Boolean ensureBearerToken, String endpointUri) +144
   Microsoft.IdentityModel.Web.WSFederationAuthenticationModule.SignInWithResponseMessage(HttpRequest request) +510
   Microsoft.IdentityModel.Web.WSFederationAuthenticationModule.OnAuthenticateRequest(Object sender, EventArgs args) +323
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +139
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +195
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +88

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.7.3930.0