IDX20803: Unable to obtain configuration from: 'https://localhost/IdentityServer/Core/.well-known/openid-configuration'

We are using the IdentityServer3.Membership library for IdentityServer. Token validation is works fine using HTTP both in Local as well as QA machine. But when we configure to HTTPS then getting below error. Steps.

Validating the token in Asp.net core 3.0 application using identityserver4.AccessTokenValidation library3.0.1 Error is getting when we hosted in IIS. and using both self signed and CA certificate Certificate is added in Trusted certificate.

Error Details:
04/16/2020 17:19:50.651 -04:00 [Error] IDX20803: Unable to obtain configuration from: 'https://localhost/IdentityServer/Core/.well-known/openid-configuration'.
System.InvalidOperationException: IDX20803: Unable to obtain configuration from: 'https://localhost/IdentityServer/Core/.well-known/openid-configuration'.
---> System.IO.IOException: IDX20804: Unable to retrieve document from: 'https://localhost/IdentityServer/Core/.well-known/openid-configuration'.
---> System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.
---> System.Security.Authentication.AuthenticationException: Authentication failed, see inner exception.
---> System.ComponentModel.Win32Exception (0x80090331): The client and server cannot communicate, because they do not possess a common algorithm.
--- End of inner exception stack trace ---
at System.Net.Security.SslStream.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, ExceptionDispatchInfo exception)
at System.Net.Security.SslStream.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslStream.PartialFrameCallback(AsyncProtocolRequest asyncRequest)
--- End of stack trace from previous location where exception was thrown ---
at System.Net.Security.SslStream.ThrowIfExceptional()
at System.Net.Security.SslStream.InternalEndProcessAuthentication(LazyAsyncResult lazyResult)
at System.Net.Security.SslStream.EndProcessAuthentication(IAsyncResult result)
at System.Net.Security.SslStream.EndAuthenticateAsClient(IAsyncResult asyncResult)
at System.Net.Security.SslStream.<>c.b__65_1(IAsyncResult iar)
at System.Threading.Tasks.TaskFactory1.FromAsyncCoreLogic(IAsyncResult iar, Func2 endFunction, Action1 endAction, Task1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean allowHttp2, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.GetHttpConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.DiagnosticsHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts) at Microsoft.IdentityModel.Protocols.HttpDocumentRetriever.GetDocumentAsync(String address, CancellationToken cancel) --- End of inner exception stack trace --- at Microsoft.IdentityModel.Protocols.HttpDocumentRetriever.GetDocumentAsync(String address, CancellationToken cancel) at Microsoft.IdentityModel.Protocols.OpenIdConnect.OpenIdConnectConfigurationRetriever.GetAsync(String address, IDocumentRetriever retriever, CancellationToken cancel) at Microsoft.IdentityModel.Protocols.ConfigurationManager1.GetConfigurationAsync(CancellationToken cancel)
--- End of inner exception stack trace ---
at Microsoft.IdentityModel.Protocols.ConfigurationManager1.GetConfigurationAsync(CancellationToken cancel) at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.HandleAuthenticateAsync() at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.HandleAuthenticateAsync() at Microsoft.AspNetCore.Authentication.AuthenticationHandler1.AuthenticateAsync()
at Microsoft.AspNetCore.Authentication.AuthenticationService.AuthenticateAsync(HttpContext context, String scheme)
at IdentityServer4.AccessTokenValidation.IdentityServerAuthenticationHandler.HandleAuthenticateAsync()
04/16/2020 17:19:50.988 -04:00 [Information] "Bearer" was not authenticated. Failure message: "IDX20803: Unable to obtain configuration from: 'https://localhost/IdentityServer/Core/.well-known/openid-configuration'."
04/16/2020 17:19:51.031 -04:00 [Information] AuthenticationScheme: "Bearer" was challenged.

Your help is highly appreciated on this.!

Resolved the issue adding below code in Startup-->Configure

ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls
| SecurityProtocolType.Tls11
| SecurityProtocolType.Tls12
| SecurityProtocolType.Ssl3;