ASP.NET Core: the first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object

Question

I am writing an app with ASP.NET Core 8, the application is a SSO using SAML 2.0. The problem is that I am not very good using C# but my work is requiring it. I managed to get Jitbit's module to handle Saml. The mistake I have is at the level of the navigal and I do not know how to solve it:

Ypeerror [err_invalid_arg_type]: The First Argument Must Be of Type String or An Instance of Buffer, Arraybuffer, Or Array or An Array-Like Object. Undefined Received

I will provide all the code that I have so far

Controller:

namespace LoginSSOSAML.Controllers;

public class LoginController : Controller
{
    public IActionResult Login()
    {
        // TODO: specify the SAML provider url here, aka "Endpoint"
        var samlEndpoint = "https://mocksaml.com/api/saml/sso";

        var request = new AuthRequest(
            // TODO: put your app's "entity ID" here
            "http://loginssosaml.us-east-1.elasticbeanstalk.com/",

            // TODO: put Assertion Consumer URL (where the provider should redirect users after authenticating)
            "https://mocksaml.com/api/saml/sso"
        );

        return Redirect(request.GetRedirectUrl(samlEndpoint));
    }

    [HttpPost]
    public Task<IActionResult> SamlConsume()
    {
        string samlCertificate = @"-----BEGIN CERTIFICATE-----
BLAHBLAHBLAH
-----END CERTIFICATE-----";

        var samlResponseString = Request.Form["SAMLResponse"].ToString();
        var samlResponseBytes = Convert.FromBase64String(samlResponseString);
        var samlResponse = new Response(samlResponseBytes, samlCertificate);

        if (samlResponse.IsValid())
        {
            try
            {
                var username = samlResponse.GetNameID();
            }
            catch (Exception ex)
            {
                return Task.FromResult<IActionResult>(null!);
            }
        }

        return Task.FromResult<IActionResult>(Content("Unauthorized"));
    }
}

The login view:

@{
    ViewData["Title"] = "SSO Login";
}

<h1>Single Sign-On (SSO) Login</h1>

@if (User.Identity!.IsAuthenticated)
{
    <p>Welcome, @User.Identity.Name!</p>
    <p>First Name: @User.FindFirst(ClaimTypes.GivenName)?.Value</p>
}
else
{
    <p>You are not authenticated. Please log in using SSO.</p>
    <a asp-controller="Login" asp-action="Login">Login with SSO</a>
}

I really need to make it work, I can't use another language or authentication mode. I am using Mock Saml to do the tests and although it facilitates the metadata I still fail to make it work