Need Cors enabled ? "Tokens issued for the 'Single-Page Application' client-type may only be redeemed via cross-origin requests"

I am trying to get an Azure token from an internal tool at work but it responds with:

statusCode: 400
ResponseBody: {
"error":"invalid_request",
"error_description":"AADSTS9002327: Tokens issued for the 'Single-Page Application' client-type may only be redeemed via cross-origin requests.
}

Code

var builder = PublicClientApplicationBuilder.Create(ClientId)
        .WithAuthority($"{Instance}{Tenant}")
        .WithRedirectUri("https://login.microsoftonline.com/common/oauth2/nativeclient")
        //.WithRedirectUri("http://localhost:8080")
        .WithDefaultRedirectUri();

var app = builder.Build();
IAccount account = PublicClientApplication.OperatingSystemAccount;
AuthenticationResult authResult = null;

try
{
    Console.WriteLine("Trying AcquireTokenSilent");
    authResult = await app.AcquireTokenSilent(scopes, account)
            .ExecuteAsync();

    Console.WriteLine("authResult = {0}", authResult);
}
catch (MsalUiRequiredException ex)
{
    Console.WriteLine("caught MsalUiRequiredException ex = {0}", ex);

    try
    {
        Console.WriteLine("Trying AcquireTokenInteractive");

        authResult = await app.AcquireTokenInteractive(scopes)
                .WithAccount(account)
                .WithPrompt(Prompt.SelectAccount)
                .ExecuteAsync();

        Console.WriteLine("authResult = {0}", authResult);
    }
    catch (MsalException msalex)
    {
        Console.WriteLine($"Error Acquiring Token:{System.Environment.NewLine}{msalex}");
    }
}

I added this line below because I was previously getting this error:

"ErrorCode: loopback_redirect_uri Microsoft.Identity.Client.MsalClientException: Only loopback redirect uri is supported, but https://login.microsoftonline.com/common/oauth2/nativeclient was found. Configure http://localhost or http://localhost:port both during app registration and when you create the PublicClientApplication object. See https://aka.ms/msal-net-os-browser for details"

''' .WithRedirectUri("http://localhost:8080")'''

I tried http://localhost also and pinged the team that wrote the tool to see what redirect they use in the azure setup.

I am new to c# so I am pretty well stuck at this point but I think I need Cors.

https://docs.microsoft.com/en-us/aspnet/core/security/cors?view=aspnetcore-3.1

I'm using ... net5.0