InvalidOperationException: Key type not specified. Microsoft.AspNetCore.ApiAuthorization.IdentityServer.ConfigureSigningCredentials.LoadKey()

As you already answered - The solution is to add the following settings into appsettings.json, within the "IdentityServer" brackets. This followed the "Clients" element:

For File

 "IdentityServer": {    "Key": {      "Type": "File",      "FilePath": "C:\cert.pfx",      "Password": "password123"    }  }

For Development (don't use in production obviously)

 "IdentityServer": {    "Key": {      "Type": "Development"    }  }

For Store

"IdentityServer": {  "Key": {    "Type": "Store",    "StoreName": "My",    "StoreLocation": "CurrentUser",    "Name": "CN=MyApplication"  }}

link

The solution is to add the following settings into appsettings.json, within the "IdentityServer" brackets. This followed the "Clients" element:

  "IdentityServer": {     "Key": {      "Type": "Store",      "StoreName": "My",      "StoreLocation": "CurrentUser",      "Name": "CN=**WHATEVER NAME YOU USED AS THE DISTINGUISHED SUBJECT FOR YOUR CERT**"    }

This follows the instructions here. Note, that this was accomplished with a self-signed certificate created with OpenSSL following this post.

From the above mentioned code , i am assuming that below line of coding is causing nullargument exception.

.AddSigningCredential(cert);

because the **cert** is null,which comes down to your method GetMyX509Certificate

try        {            System.Diagnostics.Trace.TraceInformation($"HELLO! TRYING TO GET THE CERTIFICATE");            return new X509Certificate2(File.ReadAllBytes(pfxFilePath), password, sFlags);        }        catch (PlatformNotSupportedException ex)        {            System.Diagnostics.Trace.TraceError($"HELLO! {ex.Message}");            if(sFlags.HasFlag(X509KeyStorageFlags.EphemeralKeySet))            {                return GetMyX509Certificate(pfxFilePath,password,X509KeyStorageFlags.MachineKeySet);            } else             {                return null;            }        }        catch (Exception ex)        {            System.Diagnostics.Trace.TraceError($"HELLO! {ex.Message}");            return null;        }

Since you code is not throwing **PlatformNotSupportedException** type of exception, for sure it will throwing Generic Exception which will be later catched by your last line

 catch (Exception ex)        {            System.Diagnostics.Trace.TraceError($"HELLO! {ex.Message}");            return null;        }

and from here you are returning null which internally giving you the actual error.

I don't understand why are you not able to use KUDU, but if i were you , i would suggest you to enable information logging using some logging library , e.g. File system logging or Application insighy using custom telemetry.

Hope it helps.